Fixes a lot of small things:
* zoom in/out in preview is more fine grained (use SHIFT)
* zebra scopes don't try to draw the border and fail
* lock/unlock now locks/unlocks all selected strips
* fix redraw problems of panel on lock/unlock
* buttons-panel is redrawn on translate, so that position information is shown
* added lock / hide to Strip-Menu
* fixed small drawing problems in header
TODO: find a good key for lock / unlock (Shift-L | Alt-Shift-L isn't that nice
to press...)
f59bbef4b3