Previously, image uploads were always allowed, unless `CMD_ALLOW_ANONYMOUS=false` and `CMD_ALLOW_ANONYMOUS_EDITS=false`.
This PR adds a new config option `CMD_ENABLE_UPLOADS` to configure image uploads independently. There are three different modes: `all` (everyone can upload, guests too), `registered` (only registered and logged-in users can upload images), and `none` to completely disable image uploads.
The default value is non-breaking as it is `all`, unless the config `CMD_ALLOW_ANONYMOUS=false` and `CMD_ALLOW_ANONYMOUS_EDITS=false` is set, in which case the value is `registered`.
The UI will reflect the setting and either show or hide the upload button.
Signed-off-by: Erik Michelson <github@erik.michelson.eu>