Draft: Gesture Refactor

• Refactor Gesture Directions so there is only one enum (makes gesture configuration and handling more generic)
• move gesture direction to Gesture base class
• make all gestures realtime gestures (just removes duplication)
• make all gesture types registered with one register function.
• Improve documentation inside gestures.h
• Separate trigger and semantic inside gesture. Trigger delta is the distance needed for a released gesture to be considered "completed". Semantic delta is mapped to the [0, 1] progress variable that measures how complete the action attached to the gesture should be.

These changes are being made for gesture configuration and contexts down the line, but they should be done anyway regardless of how gesture configuration gets handled.

No behavior should change.