Add partial support for Record types as method parameters
- Currently, Record has to already have been persisted on the server
Added missing support for String as a RF method return type
Fixed bugs with cast exceptions in DevMode

Review at http://gwt-code-reviews.appspot.com/780801

Review by: rjrjr@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8572 8db76d5a-ed1c-0410-87a9-c151d255dfc7