Fix 1915 : Remove the unnecessary overload from HasEditId and HasReadLink

Remove the string overload of HasEditLink, HasReadLink:
A link has to be a Uri as per OData spec.
The string overload is only referenced by a test method.
issue 1843: The context URL for a property request is not right.
The root cause is that the ODL path of ODataMessageWriterSettings is not
set correctly.
Prefer IReadOnlyList to IReadOnlyCollection in new APIs.
Fix for codeplex 1612

Support for absolute or relative URLs in CreateFix for codeplex 1612