Fix for site URL alias editing and removal

Currently, users with the alias permissions (alias.add, alias.del, alias.upd) in a site can add a Site URL (an Alias), but get an error saying they do not have permissions to modify or remove…

This feature always works for superusers since they bypass the permission check, but does not work for professors/instructors/students.

Steps to reproduce:
1. Login as the owner/maintainer of a site who has alias.add, alias.del and alias.upd permissions
2. Go to "Site Info" tool
3. Click on "Edit Site Information"
4. Add Site URL
5. Click "Continue" button at bottom
6. Click on "Edit Site Information" again
7. Clear the Site URL text from the field
8. Click "Continue" button at bottom
9. Notice Error message

Attached is a community patch which ensures AliasService checks the alias.del and alias.upd permissions properly by comparing against the /site/ permissions instead of the /alias/ permissions.

Note: a patch for the addition of aliases already exists at https://jira.sakaiproject.org/browse/KNL-296, this patch is for the editing and removal of aliases.