Updated sample editor

The sample editor needs an update.

1, the Add Plug-in meny is very messy. It would be nice to be able to filter out the plug-ins not commonly used.

2, There is still no advanced waveform editing. The pencil does what it supposed to do, but I want advanced editing with proper tools. You already have the tools needed in the fade / volume / automation editors, why not implement them in the sample editor?