UserList Improvements

-- This is my latest and last attempt with this.

Changes:
- Better GUI
- Added "Search Box"
- Added Multi-Select
- Added "Last Seen"

Known bugs:
- Date and Time are not in UTC
- Deleting ~4000 "inactive accounts" can take a while (but this is not my fault)

More important, my programming skills are not that good as I wanted, so if something is wrong in this patch - simply fix it, commit and move forward - if not leave it and use old ugly User List for another two years.

Preview:
![Lista_zarejestrowanych_uytkownikw_ 2945_pozycji _2013-03-01_14-24-13](https://f.cloud.github.com/assets/521035/209601/86ed9efe-8273-11e2-82e3-4e9fc36e2886.png)