MBS-6954: Show disambiguation comments for artist credits

Also shows the span.name-variation element if the artist credit's
credited name differs to the artist's actual name.
MBS-6996: Do not show release group disambiguation twice

The `link_entity` macro contains a call to `disambiguation` on the
entity passed in. However, `root/edit/details/merge_release_groups.tt`
was also calling `disambiguation` itself, which lead to disambiguation
comments appearing twice. Instead, simply let `link_entity` deal with
showing disambiguation comments.
MBS-7000: Tweak margins of .edit-details to avoid overlap

Now that we show `table.tbl` elements in edit details, in the edit list
this can cause an overlap with the voting buttons, as `.tbl` specifies
100% width (while the voting buttons are only floated to the right). To
work around this, I've added 18em right margin to `div.edit-details`
which is used within the edit list (but not on per-edit pages), which
causes the 100% span to extend up to the voting buttons.
MBS-6983: Correct display of the 'video' column for merge recording edits

There are two paths for rendering a list of recordings, depending on
whether or not the recording came from the database or edit data. If the
edit came from the database the display was correct, but if the data
came from an edit then the alternative code path was executed which
ignored the `show_video` variable. This commit makes both code paths
consider the state of this variable.
MBS-6952: Correctly render the 'various artists' warning

The various artists warning is shown when the "Various Artists" artist
appears in a tracklisting. However, the actual route to making this
decision is quite complicated. At the top level, this decision is made
on a per-track basis, by the track subscribing to its own artist credit
and watching it change. It seems a track's artist credit is set three
times on the tracklist page:

1. Defaulted to the release artist
2. Cleared
3. Set to the actual track artist

In the release reported in MBS-6952, the release artist is "Various
Artists", so at step 1 the warning banner is shown. However, at step 3
track artists are *not* "Various Artists" so the banner should be
hidden. However, the call to update the banner only happens if the track
artist is "Various Artists". Thus the banner can only be turned on and
never off.

Instead of conditionally updating the banner, I have removed the entry
condition - it seems that the banner update itself checks whether or not
to show itself. The logic to toggle the banner is now called from a
subscription to the track artist credits (directly, rather than
implicitly as it was before).
Merge branch 'mbs-7000' into beta
Merge branch 'mbs-6954' into beta
Merge branch 'mbs-6996' into beta
Merge branch 'mbs-6983' into beta
Merge branch 'mbs-6952' into beta

Conflicts:
	root/static/scripts/release-editor/MB/Control/ReleaseTracklist.js