remove unused code
fix inode tracker migration v3 --> v4
annotate states with cvmfs version
introduce new state id for chunk tables
fix inode tracker migration from v2 to v4
fix migration of inode tracker from v1 to v4
chunk table migration code (yet untested)
add migration testing for chunk tables
Merge pull request #650 from cvmfs/fix-hotpatch

FIX hotpatch

Due to changes to the shash::Digest class, the inode tracker and the chunk tables need to be explicitly migrated from cvmfs 2.1.19 to cvmfs 2.1.20. Done with this patch set. The migration test (integration test suite) got extended to test migration while large files are in use.