Move "readOnly" from Hyper-Schema to Validation

We move the description and schema definition of "readOnly" verbatim
from the Hyper-Schema specification (and meta-schema) to the validation
one, in the "Metadata keywords" section (along with "default", in
particular).

This addresses part of #363, which states that some keywords
historically in the Hyper-Schema specification would be better in the
Validation document. The main argument for moving keywords such as
"readOnly" is that the Hyper-Schema document could then only focus on
describing the hypermedia linking model.

Author: dlax

hyper-schema.json

@@ -115,11 +115,6 @@
                     "type": "string"
                 }
             }
-        },
-        "readOnly": {
-            "description": "If true, indicates that the value of this property is controlled by the server.",
-            "type": "boolean",
-            "default": "false"
         }
     },
     "links": [

jsonschema-hyperschema.xml

@@ -421,23 +421,6 @@
                     </figure>
                 </section>
             </section>
-
-            <section title="readOnly">
-                <t>
-                    If it has a value of boolean true, this keyword indicates that the value of the
-                    instance is managed exclusively by the server or the owning authority, and
-                    attempts by a user agent to modify the value of this property are expected to be
-                    ignored or rejected by a server.
-                </t>
-                <t>
-                    For example, this property would be used to mark a server-generated serial
-                    number as read-only.
-                </t>
-                <t>
-                    The value of this keyword MUST be a boolean.
-                    The default value is false.
-                </t>
-            </section>
         </section>
 
         <section title="Link Description Object">

jsonschema-validation.xml

@@ -740,6 +740,23 @@
                 </t>
             </section>
 
+            <section title='"readOnly"'>
+                <t>
+                    If it has a value of boolean true, this keyword indicates that the value of the
+                    instance is managed exclusively by the server or the owning authority, and
+                    attempts by a user agent to modify the value of this property are expected to be
+                    ignored or rejected by a server.
+                </t>
+                <t>
+                    For example, this property would be used to mark a server-generated serial
+                    number as read-only.
+                </t>
+                <t>
+                    The value of this keyword MUST be a boolean.
+                    The default value is false.
+                </t>
+            </section>
+
             <section title='"examples"'>
                 <t>
                     The value of this keyword MUST be an array.

schema.json

@@ -57,6 +57,11 @@
             "type": "string"
         },
         "default": {},
+        "readOnly": {
+            "description": "If true, indicates that the value of this property is controlled by the server.",
+            "type": "boolean",
+            "default": "false"
+        },
         "multipleOf": {
             "type": "number",
             "exclusiveMinimum": 0