Bugfix in transaction class

From documentation: "END TRANSACTION is an alias for COMMIT." (http://www.sqlite.org/lang_transaction.html) Removed commit()+end() commands on destructor. Also added a flag in order to avoid commit when no transactions are open.
Added possibility to define the transaction type on construction/begin.
Added missing documentation
More documentation
Added savepoint class and an accessor method to transaction class
Update savepoint.hpp

Changed license, fixed documentation
Update transaction.hpp

fixed documentation issue
Enabled c++11 flag for strongly typed enums support
Merge pull request #5 from mmickey/master

Functionality inprovement of transaction calss, also new savepoint class added