Add additional tweaks to bit crusher to make it more ipressive
* do not change depth at 16 bit, because we may have 24 bit audio in future
* change minimum to two bits
* add gain correction to avoid falling of the shelve at low bit depth
Merge pull request #255 from daschuer/bitchrusher

Add additional tweaks to bit crusher to make it more ipressive
Merge branch 'master' into goaslicer