Big refactor of SerializableTypeOracleBuilder that natively differentiates between "field serializable" and "instantiable".  Also handles covariant arrays correctly.

Patch by: scottb, mmendez
Review by: mmendez, scottb (pair program)

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1325 8db76d5a-ed1c-0410-87a9-c151d255dfc7