Investigate whether ODataAnnotable can be removed if the annotated classes are not relevent

[lewischeng-ms]

[lewischeng-ms]

Part 1: ODataAnnotatable can be safely removed from the URI parser part in the production code. Also checked that Web API doens't store or retrieve any annotation for the URI parsing. If there is no real need for URI parser elements being annotatable, we shall remove that first.

[lewischeng-ms]

Part 2: Remove all occurrences in product code (except client) that use SetAnnotation<T>() and GetAnnotation<T>(). Then remove those two methods from ODataAnnotatable.

[lewischeng-ms]

Part 3: Introduce a temporary replacement of the original ODataAnnotatable in client. We will refactor/redesign it later if there is performance bottleneck. Related issue #641