[gh-820] Add 'last updated' column to mysites list
[gh-820] Remove debug statement
[gh-820] Make the mysites table sortable using the existing unl_sites_sort()
[gh-820] Don't double up on the use of 'access' for 'last_update'

Keep them separate for clarity since they represent two different values
Merge pull request #822 from ericras/issue-820

Closes #820