Many editors have already had overlay popover implemented, but not yet the Sequencer. This patch adds overlay popovers for the 3 sequencer view modes, in consistency with the other editors.
Changes:
Overlay popovers for Preview + Sequencer/Preview + Sequencer.
Entries from the View menus moved to the popovers, which will simplify the cluttered View menus.
Additional options have been added: Show Strip Name, Show Source(ex. path), Show Duration, so users can now select what info they need to see on the strips, and get rid of the clutter.
A main switch to turn all overlays on/off has been added in consistency with ex. overlays in the 3D View.
Use full height for drawing waveforms when no info texts are displayed.
Removal of identical entries will make the code much more complicated, so it has been removed, since entries are now selectable.
Set Source text to ON and Name and Duration as OFF, as default settings, to avoid clutter and redundant Info of strips.
In the View menus, move Zoom to Fit up together with the rest of the Preview Zoom functions, to make the menus more user friendly now a lot of entries in the menus have been moved.
Waveform Displaying renamed to Waveform Display.



