Installation of SampleTank instruments (Windows/MacOS)

Just browse your system, locate your SampleTank Instruments folder and copy (or
drag&drop) all the instruments you want to add; the added instruments will be
automatically selectable. This is a very easy and fast way to load sounds.

IMPORTANT: a SampleTank Instrument is made of three essential files:

- <instrument>.sth   containing the instrument name and description
- <instrument>.sti   containing the instrument program
- <instrument>.stw   containing the instrument waveforms

They should be moved together or the instrument will not work correctly.
