new engine: Phaser4

A huge leap forward! The spectrum of sounds coming out of this thing is amazing. Congratulations Shiru, this is a real masterpiece.

I noticed a slight inconsistency between how an instrument sounds from the instrument view's PlayRow and how it sounds in the main editor, under certain circumstances. See the attached file. I guess the actual problem here is that Rest does not work with this instrument, but I like the sound that's leaking. It's possibe to force a rest by setting another instrument at the rest note. So it would actually be nice to keep the "feature", but somehow making sure it sounds the same in the preview.

P is 'pitch'. It is not really pitch per se, more like a filter of sorts, makes the sample sound more and more muffled. On some samples it actually feels like a slight pitch change, though. O is sample offset, a sample can be played not just from beginning, but starting from a later point, it helps to get more dynamics with the same sample.

A couple more issues:

- Description of the drum column layout in phaser4.txt is wrong
- There's a lot of timing drift from the drums. It seems that there is no auto-correct, but it doesn't quite add up: even if I correct tempo manually, it's still not correct.

Also, what's the proper sample rate for drums, actually?