memory (sqlite): properly wait for messages to be writen in database: the deferreds of the queries writing message to databases where not gathered and returned, so the caller was not waiting for them to continue its workflow. This was resulting in messages not always written when database was read just after the write (a case common with MUC implementation), and message was appearing empty when sent to bridge. fix 328

[D-BUS Service]
Name=org.salutatoi.SAT
Exec=sat