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.