Database: completely refactored the interfaces in such way, that any request...

Database: completely refactored the interfaces in such way, that any request will return a future called BabuDBRequestResult on which a BabuDBRequestListener can be installed. Direct inserts will automatically used if the number of worker threads is set to 0.
Checkpointer: fixed some concurrency issues.
Tests: started to make some changes to enable the tests for windows (not complete jet).


git-svn-id: https://babudb.googlecode.com/svn/trunk@183 d4c7dd96-b7b2-11dd-893d-d98698f66bbf