Move remaining feature interfaces into Microsoft.AspNetCore.Http.Features package and namespace

- #590, also related to #561
- move feature interfaces from `Microsoft.AspNetCore.Http` package
- move required classes from `Microsoft.AspNetCore.Http.Abstractions` package
- move `ISession` and `WebSocketAcceptContext` to `Microsoft.AspNetCore.Http` namespace (#590)

nit: remove transient dependencies listed in `Microsoft.AspNetCore.Http.Abstractions`'s `project.json`

Author: dougbu

src/Microsoft.AspNetCore.Http.Abstractions/project.json

@@ -29,10 +29,8 @@
     },
     "netstandard1.3": {
       "dependencies": {
-        "System.ComponentModel": "4.0.1-*",
         "System.Globalization.Extensions": "4.0.1-*",
         "System.Linq.Expressions": "4.0.11-*",
-        "System.Net.WebSockets": "4.0.0-*",
         "System.Reflection.TypeExtensions": "4.1.0-*",
         "System.Runtime.InteropServices": "4.1.0-*"
       },

src/Microsoft.AspNetCore.Http.Extensions/SessionExtensions.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Text;
-using Microsoft.AspNetCore.Http.Features;
 
 namespace Microsoft.AspNetCore.Http
 {

src/Microsoft.AspNetCore.Http.Abstractions/CookieOptions.cs renamed to src/Microsoft.AspNetCore.Http.Features/CookieOptions.cs

@@ -18,9 +18,9 @@ public interface IFormCollection : IEnumerable<KeyValuePair<string, StringValues
         ///     The number of elements contained in the <see cref="T:Microsoft.AspNetCore.Http.IFormCollection" />.
         /// </returns>
         int Count { get; }
-        
+
         /// <summary>
-        ///     Gets an <see cref="T:System.Collections.Generic.ICollection`1" /> containing the keys of the 
+        ///     Gets an <see cref="T:System.Collections.Generic.ICollection`1" /> containing the keys of the
         ///     <see cref="T:Microsoft.AspNetCore.Http.IFormCollection" />.
         /// </summary>
         /// <returns>
@@ -79,7 +79,7 @@ public interface IFormCollection : IEnumerable<KeyValuePair<string, StringValues
         ///     key is null.
         /// </exception>
         /// <remarks>
-        ///     <see cref="T:Microsoft.AspNetCore.Http.IFormCollection" /> has a different indexer contract than 
+        ///     <see cref="T:Microsoft.AspNetCore.Http.IFormCollection" /> has a different indexer contract than
         ///     <see cref="T:System.Collections.Generic.IDictionary`2" />, as it will return StringValues.Empty for missing entries
         ///     rather than throwing an Exception.
         /// </remarks>

src/Microsoft.AspNetCore.Http.Abstractions/IFormCollection.cs renamed to src/Microsoft.AspNetCore.Http.Features/IFormCollection.cs

@@ -4,7 +4,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 
-namespace Microsoft.AspNetCore.Http.Features.Internal
+namespace Microsoft.AspNetCore.Http.Features
 {
     public interface IFormFeature
     {

src/Microsoft.AspNetCore.Http/Features/IFormFeature.cs renamed to src/Microsoft.AspNetCore.Http.Features/IFormFeature.cs

@@ -3,7 +3,7 @@
 
 using System.Collections.Generic;
 
-namespace Microsoft.AspNetCore.Http.Features.Internal
+namespace Microsoft.AspNetCore.Http.Features
 {
     public interface IItemsFeature
     {

src/Microsoft.AspNetCore.Http.Abstractions/IFormFile.cs renamed to src/Microsoft.AspNetCore.Http.Features/IFormFile.cs

@@ -20,7 +20,7 @@ public interface IQueryCollection : IEnumerable<KeyValuePair<string, StringValue
         int Count { get; }
 
         /// <summary>
-        ///     Gets an <see cref="T:System.Collections.Generic.ICollection`1" /> containing the keys of the 
+        ///     Gets an <see cref="T:System.Collections.Generic.ICollection`1" /> containing the keys of the
         ///     <see cref="T:Microsoft.AspNetCore.Http.IQueryCollection" />.
         /// </summary>
         /// <returns>
@@ -73,13 +73,14 @@ public interface IQueryCollection : IEnumerable<KeyValuePair<string, StringValue
         ///     The key of the value to get.
         /// </param>
         /// <returns>
-        ///     The element with the specified key, or <see cref="T:Microsoft.Extensions.Primitives.StringValues" />.Empty if the key is not present.
+        ///     The element with the specified key, or <see cref="T:Microsoft.Extensions.Primitives.StringValues" />.
+        ///     Empty if the key is not present.
         /// </returns>
         /// <exception cref="T:System.ArgumentNullException">
         ///     key is null.
         /// </exception>
         /// <remarks>
-        ///     <see cref="T:Microsoft.AspNetCore.Http.IQueryCollection" /> has a different indexer contract than 
+        ///     <see cref="T:Microsoft.AspNetCore.Http.IQueryCollection" /> has a different indexer contract than
         ///     <see cref="T:System.Collections.Generic.IDictionary`2" />, as it will return StringValues.Empty for missing entries
         ///     rather than throwing an Exception.
         /// </remarks>

src/Microsoft.AspNetCore.Http.Abstractions/IFormFileCollection.cs renamed to src/Microsoft.AspNetCore.Http.Features/IFormFileCollection.cs

@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-namespace Microsoft.AspNetCore.Http.Features.Internal
+namespace Microsoft.AspNetCore.Http.Features
 {
     public interface IQueryFeature
     {