Completion status block shouldn't ever be blank

Reproduce problem: All users (inc students) see warnings when completion not enabled, or criteria not being set for both Course Completion Status and Self Completion blocks A user can still view a Course Completion Status block details page if completion was enabled for the course, but was then turned off site wide (accessible via the block and clicking the "More Details" link). If viewing the Course Completion Status block details page for a user not in a graded role in the course, shows the "You are not enroled as a student in this course" error message even for other users. Reproduce fix: Only users with the course:edit capability should see warnings about completion not being enabled, or criteria not being set for both Course Completion Status and Self Completion blocks If course completion is enabled for a course, but disabled sitewide show an error when viewing a Course Completion Status block details page If viewing the Course Completion Status block details page for another user not in a graded role in the course, show the "User is not enroled as a student in this course" error message rather than "You are not enroled as a student in this course". Show message in the Self Completion block if the users is already complete in the course, or has already self completed themselves.