MBS-7717: Clean up Discogs URLs with empty slug

An artist whose name consists of only special characters may be given
a Discogs URL with an empty slug, i.e. after the numerical ID there is
only a trailing hyphen: http://www.discogs.com/artist/1944002-
This hyphen wasn't removed because the relevant regex mistakenly
expected at least one character after it.
MBS-7135: Remove "/view" from Discogs master URLs

Discogs sometimes uses a redundant "/view" part in master URLs that
should be removed to get the canonical URL.
MBS-7720: Show RG ratings on release page again

Release group ratings used to be displayed (in the sidebar) for each
release in the group. When a common template for entity sidebars was
introduced in commit a059b23dfabc8f29468ba979bdb8387253aae0cb, this
feature was accidentally removed.
Add some account endpoints to the list of things with RequireSSL set.
Merge branch 'requiressl-additions' into beta

* requiressl-additions:
  Add some account endpoints to the list of things with RequireSSL set.
Merge remote-tracking branch 'chirlu/discogs_url_cleanup' into beta

* chirlu/discogs_url_cleanup:
  MBS-7135: Remove "/view" from Discogs master URLs
  MBS-7717: Clean up Discogs URLs with empty slug
Merge remote-tracking branch 'chirlu/mbs-7720' into beta

* chirlu/mbs-7720:
  MBS-7720: Show RG ratings on release page again