Change in shortcuts

Following changes in shortcuts were discussed:

Removal:

• delete all traj.
• delete all future traj.
• delete all past traj.
• open video (dbl'click)

Changes:

• Export from Ctrl+E to Shift+E
• Up/down arrow key -> not zooming anymore, but changing the selected person in show only

New:

• Shift+A: show all trajectories (disabling or toggling(?) show only)
• Shift+R: toggle recognition

This may or may not be combined with #446 (closed)