* switch focus between views with Tab
* move focus within views with WASD/HJKL/Arrows
* move focus between graph edges by holding Shift
* move focus between code references by holding Shift
* removed graph panning with WASD and moved zooming to Alt + W/S
* removed graph navigation by pressing starting character in graph view lists
* changed local reference and custom trail shortcuts
* updated Keyboard Shortcuts window
* use common back and forward shortcuts and YZ & Shift + YZ
* fix macOS issue where widgets don't get proper focus after creating a new tab
* don't use shared_ptr in QtMainView
fixes#486, #327, #214, #210
