File Explorer card

[nelsonni]

The FileExplorer card should operate in a similar fashion to file explorers available in other IDEs and applications, except for certain key functionality alterations as indicated below. The following features should be developed and integrated into Synectic:

• FileExplorer card needs to be a React component that uses the Redux store for state.
• FileExploror card needs to allow clicking on files to open a Card component containing the specific handler type for that file (i.e. clicking on foo.js should result in a new Editor card added to Redux, and therefore loaded onto the canvas).
• FileExplorer card should indicate the current git branch, and options for switching between available branches (which should result in any new files from that branch being loaded into the FileExplorer).
• FileExplorer card needs to implement content scaling for full-screen/half-screen expansion, which should result in the Card being stretched to 20% of the available width of the Canvas component.

[nelsonni]

Closed after PR #102 and #104.