Updated hand-control to emit events that are consistent with the documentation (fixes aframevr#4883)

[Clicky02]

Description: Changes the EVENTS object and getGestureEventName function to emit events that are consistent with the documentation found at https://aframe.io/docs/1.2.0/components/hand-controls.html#events. Previously, the only events emitted were gripclose, gripopen, pistolstart, pistolend, pointingstart, and pointingend. Additionally, pistolstart and pistolend were emitted when thumbup and thumbdown should have been emitted. See aframevr#4883 for more detail.

Changes proposed:

• Have the pistol events be emitted with the pointThumb animation.
• Have the thumb events be emitted with the thumbUp animation.
• Have the point events be emitted with the hold animation.
• Change the suffixes for the grip events to down/up.
• Add up/down as the suffixes for the thumb events