Audio clips implemented through scriptable object

[bottolo]

At last, audio

• Reworked the audio system. Audio sources have been distributed where needed.
• A new scriptable object, DefaultAudioTracks.cs, has been added. It contains many tracks used for various purposes, such as player feedback and level soundtracks.
• The noclip enabler zone, platform and noclip mode now have their distinct sounds.
• Footsteps have been converted to the new audio system, and they come with an interesting easter egg.
• A few placeholder clips have been added.
• A neat trick which lets you pick a custom soundtrack for a given level has been added. If there is none, a default tune will play.
• And, finally, the effects channel now serves its purpose.

Remarks

Adding clips, tracks and other effects has now become much easier and efficient. There still needs to be an actual effect system where things change when certain things happen, for example the infamous sound muffling when in noclip mode. More on that in another PR.

Improvement areas

As I've already said, effects are still not implemented. The audio mixer is cool, and provides much more tuning capabilities, but I feel that some channels are not really useful. With that in mind, channels will have to be reworked a little to trim off unnecessary parts.

[bottolo]

@spig95, take a look at that COOL AUDIO LABEL!

[spig95]

@spig95, take a look at that COOL AUDIO LABEL!

Positive reactions only