Multi-camera viewer

[jsiegle]

Create an app for simultaneously viewing streams from an arbitrary number of FLIR cameras.

The following global settings should be accessible:

• Start/stop all cameras
• Start/stop synchronized recording
• Capture one image from all cameras
• Data directory
• Layout (e.g. number of columns)

For each camera, the following settings should be accessible via popup menus:

• Custom name text box
• Serial number (select from available USB cameras)
• Exposure (max = 1000 ms)
• Gain
• White balance
• Contrast

Here's an example of what the UI could look like:

A JSON file should be automatically updated whenever any settings are changed, and should be saved along with any snapshots or recordings. This can be used to re-instantiate the exact same settings the next time the app is launched.

[jsiegle]

This is complete as of the latest PR.