Initial feature add/change/updates & hot keys

[arpgh]

Features:

• [x] Visible differentiation for annotated box vs. localization bbox
• [x] High contrast/flashy color(?) for annotation vertices
• [x] Show SNR in annotated box (wrt 256x256 patch size at scale 1.0)
• [x] Display play rate - 0.50x, 1.00x, 2.00x etc.
• [x] Annotate: mouse right-click. Select existing annotation: mouse left-click
• [x] Delete button to delete selected annotation (no backspace in Mac?) - implemented with d char
• [x] Show/hide video playback buttons
• [x] Add scale selection in data filter

Hot buttons:

• [x] e one frame forward
• [x] w one frame in reverse
• [x] v 10 frame forward
• [x] q 10 frame in reverse
• [x] f next frame forward with localization bbox for selected class(es)
• [x] r previous frame in reverse with localization bbox for selected class(es)
• [x] space pause/play
• [x] + fast-forward on each press by 1.50x, 2.00x, 3.00x, 4.00x
• [x] - slow-forward on each press by 0.67x, 0.50x, 0.33x, 0.25x
• [x] = play at normal rate (1.00x)
• [x] d delete selected annotation (by mouse left-click)

[eacharya]

Merged to development: https://github.com/zigvu/kheer/commit/7ff2d7a8644280e739d3994c2f559a1f7595023d

[arpgh]

Shall we change granularity of q and v hotkeys (and corresponding << & >> buttons) to 5 instead of 10? Since frames are currently evaluated at 5fps, this allows us to move sequentially among evaluated frames for faster mining.

[arpgh]

Done