add CMakeLists.txt.user to .gitignore

This file is generated if you edit lmms with Qt Creator.
UI: smoother knobs

This updates knobs to feel smoother and allow the user to have finer
control over the value of the knob by multiplying the mouse drag delta
by a smoothness factor.

Also since it is significantly easier to point the knob where you want
it, I removed the magnet effect. This can easily be put back in; try it
out and see what you think.
Mixer: try PortAudio backend after SDL

As there were reports about problems with PortAudio try SDL backend first.

Closes #89.
Update .travis.yml: Install g++-multilib for VST
Merge pull request #95 from Lukas-W/stable-0.4-travis

Update .travis.yml: Install g++-multilib for VST
PianoRoll: increase start key by one octave

When opening the Piano Roll for the first time and clicking on "A", you
would expect the same note that is previewed in the preview pane (A5),
but it is instead one octave lower (A4).

Fixed this by adusting INITIAL_START_KEY.

Closes #94.
CMakeLists.txt: fixed shortcut names generated by NSIS installer

Use "LMMS" instead of "Linux MultiMedia Studio" as shortcut name. This
allows to search for LMMS in the start menu on Win32.

Closes #88.
ZynAddSubFX: fixed logical error

Fixed logical nonsense reported when compiling with -Wlogical-op

Closes #80.
Merge pull request #77 from LMMS/smooth-knob

UI: smoother knobs