Implement some more sound effects and add background music in the menu.
Add one more sound I forgot to include in last commit.
The mini coin in the left upper corner now properly appear again. Also update trampoline_shot.wav (played when jumping from a bouncing tile).
Implement some functions for the Sound class to manage the sound (volume, looping, status and stopping the currently playing music). Additionally, menu music now only plays during the menu.
Add a volume manage button to left bottom corner which mutes all sounds when clicked.