UI updates

Initial UI update work to StoryTeller2:

- Fixed issue with double clicking on tree view in Tests.
- Fixed issue with switching from xml to preview.
- Removed images in favor of <a href="http://fortawesome.github.io/Font-Awesome/" target="_blank">FontAwesome</a>
- Updated status bar to turn red when there are syntax errors.
- Made nested Fixtures/Grammars turn different colors when nesting.
- Cleaned up some of the UI to be easier on the eyes (I hope).
- Cleaned up CSS.