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.
I don't think we have to follow UI capitalization unless we're referring to the UI specifically (and even then I sometimes cheat, since title caps aren't used consistently). Here, we're just talking generically about a student's user ID; if we were telling users to look at say, "the **User ID** column" or "the **User ID** value" or "the **User ID** element," we'd capitalize.