issue #363 - DEVELOPMENT: Implement Source Tab 
http://agalaldev.info/dev/mantis/view.php?id=363

- Implementing GUI and launch config save/load for:
-- Basic Cam options (cam index + frame size)
-- Basic video file options (video file path)
- Adding extensions for the Advanced options GUI section of the Source
launch tab
-- Every source can add a GUI composite that will appear in the
"Advanced options" group
-- Added a sample GUI composite for the CAM source plugin and the Vid
file source plugin
- Created AGCam Source plugin