(WIP) Studio: Adds Language Selection Menu

This works adds a language selection menu to a user's dashboard (per UI/feature request found here - https://edx-wiki.atlassian.net/wiki/pages/viewpage.action?pageId=48726317).

Status: The static assets and styles have been added, but JavaScript to manage the status/editing states as well as submit the form and save the user setting are still needed.
At minimum we should just be pulling the options directly from lms/envs/common.py so the menu is consistent with the LMS.