ui: Fix message in oops screen
Add basic access control

For now, albums can only be private or public (they are private by
default). The framework for having more fine grained ACLs is in place,
but we don't have a way to authenticate a user yet.
Update README with ACL documentation
Move hidden file skipping from monitor to thumbnailer

This allows other components to monitor hidden files.
albums: One go format fix
metadata: Ignore file events that don't concern the metadata
ui: Allow defining non-boolean parameters in hash routes
ui: Use Common.pictureUrl for map marker icons
ui: Fix invalid this usage in AlbumList
ui: Handle secret tokens for albums
Split MetadataManager into an own interface
WIP: Add groups