MMP: write to temporary file first and then rename

In order to avoid data loss because of full disks or other storage
failures write a temporary file first, rename current file to backup
file and rename temporary file to current file.

Closes #26.
New style & gfx for master vol/pitch sliders, fx front panel artwork
Effect panel & effect window style, new knob images, knobs use palette
Oops! Missing parenthesis in knob.cpp :P
Layout & bg artwork for peak controller, matching bg artwork for lfo controller & bass booster