make UI with CEGUI library
Wipe out UI type
Remove unused methods from Istate
Change MainMenu state

- store StateManager object;
- add Quit button;
- add logging;
- remove unused methods.
Fix indentation
Remove unused method from StateManager
Fix game start
Use CEGUI in StartGame state
Add layout file for MainMenu state
Fix buttons in main menu

- rename "Start Game" to "New Game";
- fix buttons positions and sizes;
Fix logging
Merge branch 'dev' into feature-use-cegui
Minimize MainMenu state scope
Add logger source files
Move boost-log includes into logger.hpp
Add function init_logging

Add two sink backends: file and console.
Change message formatting.
Make logger source local
Add named scope to log messages
Remove named scope from console logger
Use custom formatter for file logger