Add enum for envelope preview modes
Add cubic bezier-FCurves support  for envelopes
Fix envelope preview commit
Correctly preview the envelope curves
Fix some numerical issues at bezier envelopes
Fix envelope editor scaling
Clamp bezier tangents and re-fix envelope preview
Remove unnecessary debug variable
Correctly name functions, remove old code and fix bezier solver
Fix header inclusion
Merge pull request #1223 from cinaera/bezier

Add beziercurves to envelopes