An administrator should be able to hide VNC console if it's not accessible from outside

in local_settings.py an admin can set thy type of console with 'CONSOLE_TYPE', but can not diseable it.
If the console is not accessible from outside a cloud-provider's infrastructure, it should be possible to deactivate this feature in horizon.

There are several reasons one might want to deactivate the console:
- If your language has a non US keyboard and non pure ASCII characters, all the provided VNC are at best catastrophicaly unuseable.
- The network security might not provide access.