Prepping the code for a perf tweak related to incremental java compilation.
Removed registerSerializers() from FileSnapshotter because it wasn't used anywhere. If the intention is to use this method, please add it back with the client code that uses it.
Pulled FileSnapshot interface to the upper level.
Renamed one of the FileSnapshot classes into IncrementalFileSnapshot. It's not a great name but I think we should differentiate it from the other FileSnapshot.
Made the FileSnapshots travel with the IncrementalTaskInputs object. Bunch of tidy ups are pending. This change is needed to avoid extensive hashing.
Fixed a unit test.
Fixed yet another unit test that I missed during previous refactoring.
Continued the refactorings in the incremental task inputs area.
Incremental java compilation now uses the input file snapshots (mainly jars) that are coming through the incremental API. Tidy-ups pending.
Tidy-up and modelling of the FileSnapshotSet.
Small performance tweak.