Add non-volatile user settings to DB and REST service

[zfi]

If we had an additional field that could be read/written with a REST endpoint by user id, we could save a single JSON string that contains user settings/preferences.

Settings could include:

• Configure client port/host
• Terminal font size
• View in grayscale

Original issue: The "Configure Client" item under the hamburger drop down does not open a dialog unless the current session is authenticated. The menu item should probably be hidden for anonymous users.

[MatzElectronics]

We could use the same trigger used by the warning/info-text above the load/compile buttons to toggle this item's visibility.

[MatzElectronics]

I'm open to ways other than REST to do this, too.

[zfi]

Using a REST API is probably the correct way to do this if the configuration settings are going to be mobile. These settings could also be stored in a cookie but that would make the settings specific for the individual browser. I'll ponder this further.

[paragitadmin]

This can be addressed once issue #1523 has been completed.