Sleap

- Training profile params for brightness/contrast image augmentation
- Options for edge style in GUI (line/wedge)

- Single-instance inference mode
- Bug fix for gui inference on large range of frames

Bug fixes and minor changes:
- cli to sleap-track fixed
- cli to sleap-main now accepts filename to open
- bug fix to flow shift w/ color image
- bug fix when loading old trained model directory format
- bug fix to node menu for velocity-based suggestions
- moved LEAP import into menu and added missing video gui
- improvements to velocity suggestions and track trails

Fixes issue 243 and fixes "expert mode" training GUI.

TensorFlow 2-based nn code w/ cli and gui.

New gui for finding missing files, bug fixes, jsonpickle upgrade.