* adding page at /admin/config/theme-site-settings, need to show the actual (ruby?) values instead of the db values, not sure if we want to use the actual controls here…should we allow changing this in one place?
* maybe the theme-site-settings page should invert, show a list of all the themes and then the dropdown is the settings, then you can see what all the themes are overriding the values to at once? then pencil icon to edit the theme

Need to finalise controller and helper still, probably make it
easier to get "site-setting-like" conversion of values from and
to the DB, the rb_value and db_value stuff

Also send preloaded theme site setting overrides to client

Also make sure not to use SiteSetting.get here as it
throws an error -- call `current` and `defaults` directly

also adding updating setting cache and logging changes