EZ Desktop feature in SubutaiTray [PLAN]

Four major changes are required to enable the SubutaiTray with this new feature:

1. It MUST package and install the x2goclient package.
2. The E2E plugin Web Socket API needs a command message added to send the tray instructions to launch the EZ-Desktop client from web interfaces: the Subutai Hub and the Subutai Console UI.
3. The Hub and Console UI's MUST detect desktop containers and enable the EZ-Desktop button (Desktop label)
4. We need additional REST API's to be provided by the Hub - WHAT ARE THEY ? DEFINE THEM PLEASE
   • Whether a container is launchable via EZ-Desktop.
   • The Hub already provides APIs for Container object, so we can embed one more bool parameter (ex: is_desktop()) which will show if the current container has desktop with x2goserver.
5. When users select Desktop instead of ssh, (by clicking tray button or clicking button from hub and the console):
   • The SubutaiTray should execute the x2goclient with the proper parameters to establish a desktop session
   • It is better to keep EZ-Desktop feature as simple as possible, so that user can enter container by clicking only one button.

General Rules to Follow

Make most common cases require the least input or configuration. Don't confuse users. Special functions that are least used should only require configuration.