Add option to control whether unlicensed users are hidden

Confluence 5.9 filters by default all unlicensed users from mentions, the people directory, and all search selectors, as well as from search results.

In some environments, it's appropriate to still let these users be seen, so that unlicensed users are visible in:

• mentions, to help with spelling. Note that when not a user is unlicensed, these should show with a different lozenge style
• people directory, quick search and site search, to look up contact info. Note that Confluence currently does not sync phone numbers, location or other user details from external systems, so this would only really be useful today for users that have in the past had a license.

Unlicensed users should still not be selectable by default as a contributor or author. There should be a separate checkbox on the site search and cql enabled macro editor screens to allow searching for content by these users, along the same lines as the archived spaces search option.

Unlicensed users should never be available as a target of a space permission or content restriction. Users need must be licensed before they can be assigned these.