MIN: Minor edits in the documentation website.
DOC: Minor changes in the documentation website.

Including how to export an appliance, updated links to course materials,
reworked the known issues, and added a link to known issues from the
quickstart.
Merge remote-tracking branch 'upstream/master'
DOC: Decribe the procedure to build 32-bit images.
MIN: Update to most recent Radx version on Radx provision script.
Merge pull request #4 from heistermann/master

Update documentation website.