Fixes: DOC-599

and new column in anonymized csv, and applies image standards to all image files in this chapter.
@adampalay , @sarina the addition of the User ID column came out of LMS-2791, please check for accuracy.
@srpearce , @mhoeber please copy edit and proofread.
Decapitate "Anonymized User" and "Course Specific Anonymized User" (see above comment); add hyphen in "course-specific"