DATAREST-221 - Improved return type matching in ProjectingMethodInterceptor.

We're now using Spring's ClassUtils.isAssignableFrom(…) to make sure we match primitives and wrapper types as well.
DATAREST-150: Add test case showing PUT now works correctly.

The JIRA issue asserts that PUT wasn't properly storing things. But now it does. A partial record causes all other fields to get nulled out. I added a test case to confirm this.