Increase the volume of OpulenZ, because it is very very quiet and it's better to correct this now before 1.0.0 is released
Piano widget: make keypresses (gui and keyboard) based on the MIDI base velocity spinner
Do the opl amplification smarter
Envelope: fix drawing of envelope graph, scale to fit view if graph gets too long
(also fix typo in last pianoview commit)
Merge pull request #500 from diizy/stable-0.4

Piano widget: fix velocity, Opulenz: increase volume