ensure that only administrators can get to the admin pages
add tablesorter jquery plugin
wire in the table sorter
make the table sorter a bundle
tidy up the code for bundling packages
don't make the header section required
put the total number of sessions at the top of the page
few minor style tweaks
remove the tablesorter from NuGet as it is checked in

(because the NuGet package drags in other stuff we don't need)
Make sure the minified file gets included instead of created
remove some of the custom style and use the bootstrap-provided ones
Merge branch 'admin-sessions-page' of https://github.com/adrianbanks/dddeastanglia into adrianbanks-admin-sessions-page
Merge pull request #82 from adrianbanks/admin-sessions-page

Work on the sessions page in the admin area. This add some styling to the table
of sessions, as well as the ability to sort the table.