add record placeholder icon
add record icon to icon bank
implement record mode
follow playback cursor in record mode
stop recording on silence button
Merge pull request #259 from cyberixae/implement_recording

Implement recording
Add first iteration of module saving task.
Store module path in session.
Implement default task executor.
Add saving support to the module object.
Add save button.
Set command line module path as the save target.
Rewrite task execution, disable UI when saving is in progress.
Move module loading and sandbox creation to the module model and root view.
Support token bouncing in the audio engine data setter.
Support flushing of transactions pending validation in store.
Flush store before saving.
Keep save button disabled until loading has finished.
Use save dialog when saving a new composition.
Clean up.