Add exceptions for Lombok annotations to UnusedPrivateFieldCheck

(S1068). Class- and field-level annotations are checked. [Lombok](http://projectlombok.org/) generates methods and constructors from annotations, eliminating boilerplate code. Source-level analysis should take into account Lombok semantics to prevent false positives.

Test case fails for reasons I don't understand. If I drop the "lombok." prefix on the annotation names, I can make the test pass. Why doesn't the annotation's `IdentifierTree.name()` return a fully-qualified annotation name?

An alternative implementation would be to sublass this check and allow Lombok support to be turned on/off on a per-project basis.