removed dbconnection from databasefacade
implemented select on database facade
implemented retrieval functionality on documents class
implemented update on documents
added contains functionality to documents and extracted interface for documents
added transactional command executor
added abstract database facade as base class for test doubles
implemented delete on documents
WIP: added construction test
implemented working end-to-end write test
added test for transactional command executor
added retrieve to end to end test
added delete by id
added tests for selects from database facade
added test for documents.contains
added test for delete
added tests for store
added test for default command mapper
added tests for read-commands on command executor
added test for contains on database facade