New SF2 plugin artwork
Final tweaks to SF2 artwork (based on feedback), moved chorus & reverb buttons a bit to fit them better with new artwork
New led graphics, initial style sheet changes (work still in progress), other theme changes
Stylesheet changes, added palette customizability, fx mixer obeys palette, etc...
Fixed typo :P
Merge pull request #24 from diizy/stable-0.4

Merge for now and let's fix things later.