Updated Rendering of menu items to use RenderingItems

-Deleted the now unused SDL_Texture/SDL_Rect
-Replaced code to use the RenderingItem equivelent.
-Minor changes to initialization of greyArea
-Moved initialization of menu items to separeate method
Changed rendering of menu.

-Split rendering of lobby footer into separate method
-RenderMenu() now first renders the menu items common for both main menu
and lobby
-RenderMenu() calls either RenderMainMenuFooter() or RenderLobbyFooter()
    depending on GameState
Renaming of variables

-Renamed fullscreen to isFullscreen
-Renamed ml( MenuList holding all games ) to gameList
-Updated code to reflect above changes
Added Init() to RenderingITem

-Init() takes a SDL_Renderer and a color
-Inits texture by filling it with color
-Uses method in RenderHelpers and SDL_Rect already in RenderingItem