Email message text for content outside of a group

Currently content-related activity stream messages add the "into groups x y and z groups" text by:

- Commons_groups alters message types defined by Commons Activity Streams, adding a [commons_groups:in-groups-text] token to the message in the 3rd partial field.

However, the message types in Commons notify tend to assume that content will be posted into a group and include a group title token in the subject.

We should figure out a plan for content that is not posted into a group, such as a site-wide notice.