Merge branch 'master' of github.com:olegabr/framework into feature-261
Database and cache dissynchronization after transaction rollback fixed

 * The idea is to substitute a temporary cache object for the QApplication::$objCacheProvider in a TransactionBegin call. All objects written in this temporary cache object would be dropped in a rollback and written in an actual cache on a commit. The actual cache object would be restored in both roll back and commit calls.
 * A test suit is added to prove the implementation.
Merge branch 'master' of github.com:olegabr/framework into feature-261
Multiple database embedded transactions support is added

The case if there are transaction of one DB in the middle of the transaction of another DB.
The replay function is enhaced
Documentation for QDatabaseExceptionBase is added.
Merge pull request #270 from olegabr/feature-261

The fa34bd8 commit is the one I've missed here. But it is already there.