Show tag count that corresponds to viewer's permissions

[cmshaw]

Title
Show tag count that corresponds to viewer's permissions

Short, concise description of the idea
This is a technical change to S2's TagDetail.use_count information, requesting that it reflect the permissions of the viewer.

Full description of the idea
The use_count member of a TagDetail object returns the number of times this tag has been used in total, including uses that the viewer does not have permissions to see. For example, a tag with one public and five private uses will always have a use_count of 6, even viewed after logging out.
An ordered list of benefits

• Tag counts may not be particularly sensitive information, but they deserve the same security settings as everything else.
• Also, a count of tags visible to the viewer is, I would think, what most people expect from use_count.

An ordered list of problems/issues involved

• The page designer could be able to tell what security level the viewer had by reading the count of visible tags.
• It might be more of a database load.

An organized list, or a few short paragraphs detailing suggestions for implementation

• Either use_count could be changed to show only a count of visible tags or a new member (visible_count?) could be added to the object.