SF2: Fix loop offsets + tuning

[MyBlackMIDIScore]

Added the coarse offset and looping SF2 zones and fixed support for loop offsets and fine/coarse tuning.

Should fix #80

[MyBlackMIDIScore]

Why did clippy just remember those unused functions wtf

[arduano]

idk what the implementation details are but lgtm

[arduano]

I'll figure out clippy

[MyBlackMIDIScore]

idk what the implementation details are but lgtm

I only added support for some SF2 generators (equivalent of opcodes for SFZ) and how some existing ones were parsed because it was wrong. I tested it and it works fine so dw

I'll figure out clippy

Should I wait for your PR about clippy to be merged or are you going to do it afterwards?

[arduano]

Weird, I wonder why the changes of my last PR show up in this PR as well

[MyBlackMIDIScore]

Weird, I wonder why the changes of my last PR show up in this PR as well

I merged master in sf2-fixes before merging this PR to avoid conflicts, so it shows your commits here. Although in master it doesn't show that I wrote any of your changes so it's all good.

[arduano]

Yeah usually github is supposed to hide duplicate changes from PRs, it's not supposed to show master's changes in your branch when you update from master, kinda strange but oh well