Split forms for environment variables and Ant/Maven/JDK installations

As discussed on the dev list: http://www.nabble.com/Splitting-up-the-Installations-form-t4375197.html

I think the form for adding a new Installation should be split up into one form for environment variables, and another for the Ant/Maven/JDK installations.

The current web UI is confusing, we have a field marked as required when it usually isn't, necessitating a long field label to try to explain the situation.