MDL-18229 gradebook: Initial commit of LSUs Quick Edit Plugin

Renamed to Single View in MDL-47289.
MDL-18229 gradebook: Added filter icons for activities and users.

Corrected CSS for grades column, was far too large.
MDL-18229 gradebook: Single view navigation corrected.

Usernames link to user profiles.
Activities to their activity page.
MDL-47347 added basic navigation to top and bottom of gradereport_singleview
MDL-18229 gradebook: Linking activities and usernames correctly.

Activities to their course page and usernames to their
profile page as per standard.
MDL-18229 gradebook: Fix for loading activities.

Was using local variable iteminstance rather than cmid.
MDL-18229 gradebook: Renaming of Single_view to Single view
MDL-18229 gradebook: Links to Single view via icons on Grade Report.
MDL-18229 gradebook: Updating code to Moodle standard.
MDL-18229 gradereport: Labels for table items added.
MDL-18229 gradereport: Behat tests added.
MDL-18229 gradereport: Fixes and improvements from review.

Added pagination back in with some general fixes.

AMOS BEGIN
 CPY [override,mod_quiz],[override,gradereport_singleview]
AMOS END
MDL-18229 gradereport: updated index.php test to calculate navigation based on new class name 'gradereport_selectable_items'
MDL-18229 gradebook: Additional fixes.

Random foo left in options. (test code)
Allowed editing link for Course total.
Fixes based on Apu's review.