Bug 1623 - Provide view of approved comments

Bug 1623 - Provide view of approved comments

This patch creates two tabs on the comments administration page:
one for approved comments and one for unapproved comments. Each
display is paginated according to the numSearchResults preference.
The list of approved comments has, instead of a link to approve,
a link to unapprove.

The JavaScript table sorter has been removed since it doesn't make
sense to sort individual pages of a multi-page result set.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>