Flask refactor

[wjwwood]

Ok, so... I just wanted to implement https://github.com/ros-infrastructure/prerelease_website/issues/38, but then:

• I needed to change the way the ajax worked, but
• that exposed a bug in Dajaxice (django plugin for ajax stuff), and
• Dajaxice is no longer supported (for almost 4 years), so I want to try another django plugin, but
• it needs a newer django, but
• our project here doesn't support anything newer than django 1.6 (released in 2013), but then
• I couldn't get django 1.6 working with my version of Python 2.7 and in general had trouble setting up a dev environment, so then
• I realized we didn't actually need django, so I converted it to Flask because
  • it was simpler,
  • used the same template engine,
  • and had a nice tutorial for ajax

So this pr:

• converts to Flask from django-1.6.x
• removes use of Dajaxice for jQuery's $.ajax
• removes old parts of the website left from pre-indigo
• rewrites the setup instructions

I've deployed this on the web server because I had to figure out all the little details with virtualenv and newer versions of catkin_pkg and ros_buildfarm. I'm waiting on OSU to deploy the updated apache configs, so it might be unstable for a bit. I'll keep refreshing the settings until they do that.

I don't think this needs review, but I'm putting through a pr for posterity. However, reviews are welcome.

[tfoote]

A spot check with indigo showed it working for me at the moment.