Rename Socket.cpp
Added server login
Changed IMPacket to make it easier to use. Completed load allocation
logic in EpollThread.
TODO: Session-Channel-Conversation must be completed before higher level
implementation
We need a SQLCache or something like that to interact with database.
Mutex must be well designed or else it will be a threat to performance.
Added DBCache as mediate between app and db.
Added sql support in project file
Added test skeleton for DBCache.
TODO: More implementation needed