Initial less-colors work from June.
Change @header-orange and @header-purple to @musicbrainz-orange and @musicbrainz-purple.
Rename @diff- to be clearer
Purge @re-addtrack-text, replace with @placeholder-grey
Remove @form-error-text, merge into @negative-text.
Merge @moved-cover-art-bg into @diff-new-highlight, as it's essentially just a diff.
Purge @re-unfocus-tab-text and @re-focus-tab-text, replacing with musicbrainz-purple and text-orange. Will fix up icons to the same purple in a separate commit.
Update (track|)-(up|down).png, expand.png, and collapse.png for color change.
Merge branch 'beta' into less-colors
LESS colors: greygreygreygrey
Merge branch 'beta' into less-colors

Conflicts:
	root/static/images/icons/collapse.png
	root/static/images/icons/down.png
	root/static/images/icons/expand.png
	root/static/images/icons/track-down.png
	root/static/images/icons/track-up.png
	root/static/images/icons/up.png
Image optimization.
Initial attempt to merge greys.
Allow creating entities from the inline search
Require RG, AC, and labels in release editor now
Remove the relationship editor's WorkDialog
Merge branch 'beta' into entity-dialogs
Fix condition to allow adding catalog numbers without labels
Merge branch 'beta' into entity-dialogs
Merge branch 'beta' into less-colors

Conflicts:
	root/static/styles/layout.less
	root/static/styles/relationship-editor.less
	root/static/styles/release-editor.less