Experimental Build - Command Stacking

I've added a v2 experimental build that has a new command stacking feature. This allows users to run some commands asynchronously (in parallel) by either selecting "Run Async" in the Properties Inspector to clicking and dragging the commands together. 

CAUTION: This is an experimental feature that may make things unstable or unreliable. User carefully. From my personal observation, selecting the Async option in the inspector is more reliable than drag and drop at this time. I will delve more into this tomorrow.

Also fixed a bug that kept videos as image elements in the UI from playing in built games.