Fix for Issue 615: reverse swapped Class.isAssignableFrom calls in Mapper.isCompatibleForOperator

Broken up into 6 commits in decreasing order of importance.  Just the first commit 417da9a would be enough for our use case as described in Issue #615.  The second fixes a related but probably less common issue.  The third fixes an issue that will probably never come up in practice but should be fixed for completeness.  The fourth commit ac19bd9 makes no functional changes but cleans up some warnings by adding a type parameter to Arrays.asList() calls in that same method.  The fifth works around a strange Java 6 compilation error from the fourth, and the sixth commit fixes an unrelated checkstyle error that shows up on my machine when building with Java 6.

I think all 6 are valuable additions, but if it would help get the pull request accepted more quickly, I'm happy to resubmit with just the first commit.