Add the ability to create a custom font lists centrally

[mararad]

Add the ability to create a custom font lists centrally and for users to be any to select any or none of them.
The UI for creating and editing the font lists can just be comma separated forms with another form for the name of the list.
In the first iterations allow one font list to be created and for all users to use it regardless. When inserting via velocity templates always assume the template might fail to create the global variable, test for it in the same way COMMERCIAL_LICENSE is tested for. And preview these global variables with something like comMxgraphVelocityGlobal just to avoid any possible clash.

See https://answers.atlassian.com/questions/295755/export-draw-io-to-pdf-or-png-changes-used-font

[stale]

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