add CU_CLONE_USABILITY_MISMATCHED_RETURN, and don't report return types that instanceof this's class
add fp for chained calls thru a field on different base objects
fix fp for chaining thru a field access
add valid chaining case
Merge branch 'master' into test

Conflicts:
	etc/findbugs.xml
	etc/messages.xml
	samples/CU_Sample.java
	src/com/mebigfatguy/fbcontrib/detect/CloneUsability.java