Implement Trimming Support

[dustin-lunarg]

Currently, the capture layer will capture all frames from application start to exit. Add support to the layer for capturing a range of frames, as well as a utility for trimming existing capture files to a sub-range of frames.

This feature will be implemented with the following sub-tasks.

• Implement State Tracking for Trimming (Implement State Tracking for Trimming #182)
• Implement Trimming in the Capture Layer (Implement Trimming in the Capture Layer #183)
• Implement a Trimming Utility (Implement a Trimming Utility #184)

[dustin-lunarg]

The initial trimming implementation is currently available on the dev branch.