Main Menu (updated)

Description:

Main Menu is the UI menu design, which is the red thread for all the menus.

Dimensions:
 * Menu is centered on the screen
 * Credits button is located down in the right corner of the screen
 * Menu is surrounded by the round Terra Nostra Logo
 * It is divided in to 3 buttons
 * Top button is larger than the  2 buttom buttons
 * Above the coloured rim the charather in sillouet will walk (part of logo)
 * Above the coloured rim the game name "Terra Nostra" (part of logo)

Functionality: 
 * "Start" change to "Resume" under the in-game menu
 * "Exit" change to "Exit to menu" under the in-game menu

Aesthetics:
 * Buttons should have stone texture, similar to the UITimeline textureEngravedStone.png
 * The letters should be engraved
 * The background in main menu is a white gradient that darkens along the side

Animations:
 * Buttons clicked:  button darkens
 * Entering game (Play is pressed): Fade to black.
 * The charather in sillouet will walk on top of the circle
 * The colours of the outer rim rotates anti-clockwise