Add basic Unity interface (Real Merge Request)

Description

The primary purpose of this merge request is to update the Unity interface. It also includes some cleanup.

• Moved RobotActivationDeactivation and RobotConnection scripts from Unity games to here
• Combined the above two scripts into one script that persists throughout an entire game
• Fixed the coordinate transformation between robot coordinates and Unity coordinates
• Updated the interface and added documentation
• Renamed bt namespace to Barrett
• Removed the unused UDP client
• Moved parts of RobotController from Unity game to here

What to focus on

• Please concurrently review the corresponding merge request https://git.barrett.com/software/burt-haptics-demo/merge_requests/3
• ProficioClient/UnityInterface/RobotConnection.cs
• ProficioClient/pg/PropGroupRobotApp.cs (lines 95-96, the rest is namespace changes)

Reviewers

• @heather
• @cw
• @amyblank
• @bz
• @jchung
• @ps

Resources

See !4 (merged) for issues created by @amyblank

Issues

• Fixes #6
• Fixes #7
• Fixes #14
• Fixes #23