Make sure meta boxes are added to Venue edit screens when localized.

Localizing the "Gigs" string changes the venue edit screen id, which
caused the meta boxes to not appear since they were using a static id.

Also add a couple of missing i18n wrappers on meta box titles.
Update the Grunt makepot task.
Bump to version 1.6.2
Merge updates from 1.6.2