Improve user/admin experience with aws configuration

[aashish24]

• Nice to have: drop-downs for Availability zone. Currently a user has to enter this manually.
• Nice to have: ami list shown to the user given his/her zone.
• Nice to have: Suggestions for Cluster User
• Nice to have: Enable users to launch instance while the setup is running (in case something goes now). Currently you would have to wait until the process is done. This could be a problem if the process is stuck somehow.

[matthewma7]

Is this still within the scope of current Minerva?