Improvements to Kicker (work in progress)

I've made some new changes to Kicker, making it usable for more than just kick drums.

A list of some new features:
* Pitch slope (how fast the pitch goes down)
* Volume slope
* Start and end points can use the played note, making it usable as a melodic instrument
* Decay changed to Length, and maximum increased to 2 second
* Noise can be mixed in to the sound, making it usable for snares and hihats for example.

Still missing proper new artwork (will come later).

[Here's a demo of what it can do.](https://soundcloud.com/greippi/testing-the-new-kicker)