Enable h2 concurrent db access.

By setting AUTO_SERVER to TRUE multiple processes, e.g. the application itself and a SQL client like Squirrel SQL, can concurrently access the h2 database. More information: http://www.h2database.com/html/features.html#auto_mixed_mode
Removed uncommented and unused config.
Merge pull request #22 from buehner/h2-concurrent-access

H2 concurrent database access