Permission fixes

Managers need to be able to see reports; block needs to be able to be added to the site homepage so that it can be "sticky" throughout site.
Prevent dev mode reset from running if not in dev mode

Otherwise, anybody who can find the URL can run the reset.
Skip generating stats for site course

We're not interested, and there's nothing to see anyway other than accesses.
Remove closing PHP tag from version.php
Use correct string for "Resources: Resource details on students" report title
Make Gismo options user-specific

Since we use a site-wide instance of the block, instance-specific
options are not at all useful.
Use $CFG->wwwroot rather than constructing relative path

The relative path only worked on certain page levels (i.e. course main and
section pages).
Report ungraded assignment submissions as having grade of -1

This allows the chart to display an empty red rectangle to show that there
is an ungraded submission, rather than leaving the square entirely empty.