Refactor DartdocConfig option usage, part 4 of 4 (#1676)

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* Refactors complete, linkups integrated, tests pass

* Delete old tests

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Author: jcollins-g

README.md

@@ -103,13 +103,29 @@ generates docs.
 ```yaml
 dartdoc:
   categoryOrder: ["First Category", "Second Category"]
-
 ```
-For now, there's only one option:
+
+Unrecognized options will be ignored.  For now, there's only one supported option:
 
   * **categoryOrder**:  Specify the order of categories, below, for display in the sidebar and
     the package page.
-  
+
+The following are experimental options whose semantics are in flux and may be buggy.  If you
+use one, please keep a close eye on the changing semantics.  In general, paths are relative
+to the directory the dartdoc_options.yaml the option is defined in and should be specified
+as POSIX paths.  Dartdoc will convert POSIX paths automatically on Windows.
+
+  * **ambiguousReexportScorerMinConfidence**:  The ambiguous reexport scorer will emit a warning if
+  it is not at least this confident.  Default: 0.1
+  * **examplePathPrefix**:  Specify the prefix for the example paths, defaulting to the project root.
+  * **exclude**:  Specify a list of library names to avoid generating docs for, ignoring all others.
+  * **favicon**:  A path to a favicon for the generated docs.
+  * **footer**: A list of paths to footer files containing HTML text.
+  * **footerText**: A list of paths to text files for optional text next to the package name and version
+  * **header**:  A list of paths to header files containing HTML text.
+  * **include**:  Specify a list of library names to generate docs for, ignoring all others.
+  * **includeExternal**:  Specify a list of library filenames to add to the list of documented libraries.
+ 
 ### Categories
 
 You can tag libraries in their documentation with the string `{@category YourCategory}`, and