Refactoring, introduction of MenuComponent and MenuScreen.
- screen components moved to a separate source file
- screen components can now be appended to any element on the page
- game class moved to a separate file
- MenuComponent and MenuScreen introduced, main menu is now built up by javascript at initialization
- initialization moved from index body onload event to be directly (earlier) executed in armada.js
- screen components' HTML files no more get fetched every time their screen reloads