Merge pull request #155 from jweather/master

fix *_slide_shape validations
Merge pull request #156 from jweather/master

make links in Info pane clickable
Default random generator seed in all new threads to 0

* This makes the random streams to be much less tightly coupled allowing 
  you to move threads around in a composition without affecting the 
  stochastic aspects of the sound due to random generator differences.
* Give in_thread a :seed option to allow the explicit specification of
  a seed for the new thread:

  in_thread seed: 2 do
    puts rand #=> 0.436 
  end
Correct name of group - it’s the RP System Volume
whitespace fixes
Add force mono mode to advanced audio prefs
add mixer_force_mono to mainwindow.h