Adds a file selector for use with the export button.
Enabled adding multiple selected requirements at once

Added functionality to allow all highlighted requirements to be added over at one time. For example, if 3 requirements are highlighted, and the '>' button is pressed, those 3 will move over.
JTree changes:

	- It should update properly at all times, placing games in correct folders.
	- It should stay comfortably wide enough to read.
	- It should be fully expanded by default.
Merge pull request #159 from austintrose/sbl-dev

Game tree changes: