Fix memory leak
Add bulk of new implementation

- Removed unused variables
- Added code to copy non-video tracks to outputComposition (yay audio, subtitles, etc.)
- Added untested logic to insert 2x video tracks at 1 frame offset
- Added code to create instructions
	- Going based on Apple's AVCustomEditOSX example
	- First we `alloca` all timeranges and calc
	- Then we create all of our instructions