New Postgres driver.

Fix for State check. Postgres driver was throwin exception for disposed connections when accessing state.
Mono update. Previous version of Mono didn't work on Linux. This one should.

TODO: test if now Mono version works without removing Mono.Security
Number counters minor changes.

Counters are used to create temporary unique simple identifier
(as convenience, not requirement - thus no locking guards).
Since this can be used on various objects, rename EntityKeys -> NumberCounter