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;
Merge branch 'dev' into feature-use-cegui
Minimize MainMenu state scope
Merge branch 'dev' into feature-use-cegui

Conflicts:
	src/main.cpp
Fix logging in main_menu_state.cpp
Add method IState::name()
Add logging into IState childs
Add method StartGameState::name
Add method MainMenuState::name
Fix indentation
Add method StateManager::inject_time_pulse_