Issue #31: cache interface, test and void impl
Issue #34: FIFO impl, tests and storage manager

Implemented FIFOVMCacheManager, covered it with tests and integrated
with GlobalStorageManager. There are TODOs left which will be
implemented later.
Issue #31: integration tests and refactoring
Issue #31: Integrated cache manager with CWS.

Note that the integration code is awfully ugly, but I had to follow
mequrel's style (which fortunatelly will be changed soon).
Merge pull request #32 from malawski/bryk-storage-enhancements

Cache support.