Implement markdown notes for Host, VMs and Jails

[yaroslav-gwit]

This feature will be a part of my current effort to release a new version of the WebUI. The tiles below will support markdown, so one would be able to create a beautiful-looking notes for any resource available.

Eventually I may add this functionality to Networks, Datasets, Templates, etc.

Jail:

VM:

Host:

[yaroslav-gwit]

Host is now done:

Will have to do something about the most common error state: if the markdown file isn't there (doesn't exist).
This edge case (affecting older installations) will likely be handled by the front-end.

[yaroslav-gwit]

The feature has been implemented for a while now, with the error case handled such as below: