enhancements for backup and restore, ssh keys

- versioned docker image
- use supervisord to launch processes in docker container
- implemented restore of user files into docker container
- generate ssh keys for user inside the docker container
Merge pull request #18 from tanmaykm/tanmaykm

enhancements for backup and restore, ssh keys
replaced nginx with tornado in docker image.

- resulted in smaller image size (tornado was already installed for ijulia)
- implemented file upload/download and directory browsing with tornado
wait for shell to start before ponding to browser.
also removed (hid) the option to re-create a session from the login screen to simplify the screen.
synchronize git repos. admin enhancements.

- added sync tab with ability to synchronize git repositories on to juliabox
- enhanced admin/account tab to display ssh public key (for git authentication), juliabox version.
- allow user to upgrade juliabox image
Merge pull request #19 from tanmaykm/tanmaykm

git sync and other enhancements
GDrive browser side integration. Refactor JS code.
google drive sync. miscellaneous changes & fixes.

- google drive sync
- refresh button for file browser
- corrected regression in setup.sh script and docker build script
- corrected script urls to take the same protocol as the parent page
Merge pull request #20 from tanmaykm/tanmaykm

google drive sync. miscellaneous changes & fixes.