Show / Hide add-ons header task is done
Reason found.
Merge pull request #117 from vmoyseenko/DUI-AddonsHeaderHiding

Show / Hide add-ons header
Merge pull request #119 from vmoyseenko/DUI-HoveringAtAnyPlaceShouldTooltip

DUI: fix appearance of tooltip.
Merge remote-tracking branch 'remotes/origin/Sitrus2' into DUI-AddonsTVRemoveScrollViewer
AddonsTreeView control is created
AddonsTreeView control is used in LibraryView and LibrarySearchView
AddonsTreeView datatemplates are moved to usercontrol's resources