'Mute' doesn't mute all sounds

[lauracumming]

Describe the bug The mute button only mutes sounds from the actual game window (van starting, van crashing, success sound, fail sound etc), but not the sounds from the Blockly window - so even when muted, the blocks still click when they're put together and the bin sound still plays when the blocks are deleted.

This is probably because our mute button only affects our own custom sounds and not the ones from the Blockly library.

To Reproduce Steps to reproduce the behaviour:

1. Go to any Rapid Router level with blocks (example, level 3)
2. Click on the Mute button.
3. Drag some blocks and hear the clicking sound.
4. Remove some blocks / Bin some blocks and hear the bin sound.

Expected behaviour The mute button should mute all sounds, including the ones from the Blockly library.

Good places to start

• Mute function: https://github.com/ocadotechnology/rapid-router/blob/master/game/static/game/js/game.js#L632
• Sound module: https://github.com/ocadotechnology/rapid-router/blob/master/game/static/game/js/sound.js