Add ability to generate additional [wiki:username] links for each user

[Matt Callaghan]

Our configuration of trac has every user their own wiki page (mostly for contact details and the like). i.e.:

List of users:
 * [wiki:username1]
 * [wiki:username2]
 * [wiki:username3]

The ability to pass in a parameter to the UserStatsMacro to allow such generation of links would replace that hard coded list ;-0

Example UserStatsMacro call:

[[UserStats(wiki=$username)]]

might generate wiki text like:

|| User || Last Login || How long ago ||
|| [wiki:user1] || 2008/12/08 21:07:58 || <24h ||
|| [wiki:user2] || 2008/12/02 22:02:40 || 6 day(s) ||
|| [wiki:user3] || 2008/12/06 16:38:27 || 3 day(s)  ||

i.e.

User	Last Login	How long ago
user1?	2008/12/08 21:07:58	<24h
user2?	2008/12/02 22:02:40	6 day(s)
user3?	2008/12/06 16:38:27	3 day(s)