Added a bunch of the "synth" patches

[asikwus]

I got inspired to recreate some classic GM synth patches, without this in mind actually. But when I found out about this project, it was like they were destined for this. The samples they're made with are either the sfz 2.0s internal waveforms or completely original sounds, made from scratch with OpenMPT, Audacity and the synth-plugin Vital.

I quickly ported over some of them and designed some more on the spot, like Synth Strings 2, Lead 1 (square), Lead 2 (sawtooth) and Pad 3 (polysynth).

There are problems with the absolute cutoff values on the filters and the panning in current bank-file, which are not present in the individual preset-files. I dunno how to fix that.

Also, many of them are using the same samples but with respective clones in their sample folder, which is unnecessary waste of space. I think there should be a sample folder called Common where samples shared by multiple instruments can be located.

[jlearman]

Thanks for doing this. Sorry I didn't see it earlier. I'll review this week or next. Feel free to post back if I forget.

[jlearman]

Regarding files shared by multiple instruments: one option is to simply use samples from another instrument, rather than duplicating them. I'll look into doing that.