option to ignore feedback detection - /i know what i'm doing/ mode.

This currently only has effect if the loop connection is
made/unmade while the option was set/unset.
Toggling the option itself won't trigger a graph re-order
Revert "option to ignore feedback detection - /i know what i'm doing/ mode."

This reverts commit e17f75b351356279778e4ea4adbb6c0d544ba755.
update linux packaging script to include xjadeo & harvid
add script to install video-tools
refine video-tools installer:

* arch/platform detection
* curl progress-bar
redesign toggling of editor/mixer stacking to use Gtkmm2ext::VisibilityTracker
Merge branch 'master' into cairocanvas
do not lower waveforms to the bottom of their group - they are supposed to be above the time axis view item frame, not below it