New level, collectables, background, ui and minor changes to the player and menu

-New blue parallax background -New level in-progress to test the player -New animated collectable coins and hearts -Slightly changed player camera to adapt to the new level -Slightly changed menu to initiate directly the new level instead of the test level -Added class, signals and functions to player script that allow the collection of coins and hearts -Added new UI layer that counts the number of collected hearts and coins