Volume: change 'chunk size' from 1GB to 16MB and disable incremental allocation. The 'full chunk allocation' option was removed and is now on by default.

This change completely changes  storage format, there is no backward compatibility with previous versions.

This solves race conditions while byte[] was being copied inside in-memory store. It solves issues #302 and #303
Maven:  do not run tests in parallel, it causes out of memory errors
StoreWAL: do not delete log file after every commit, keep it around so commits are faster