ConnectionManager and Callbacks interfaces added.
@TODO Issue with unreleased SQL connection in ConnectionManager class exists.
Connection manager creation improved. DropItems addition and deletion from Database added.
ConnectionManager implementation + DropItem imprv + TC imprv

GetDropItem method implemented and testes
New method required in DropItem added (required by ConnectionManager)
TC improved, a new test related to GetDropItem added
New method to ConnectionManager class added.
Code cloning removed in ConnectionManager (query).
Platform impedency provided, ENVIRONMENT_BITS defined.
Test cases improved.
Initial version of DropCore is implemented and tested.
All tests pass.