Standardize on 'My' for user pronoun labels

Standardize on 'My' for user pronoun labels

The TPAC currently uses a mish-mash of 'My' and 'Your' when
labeling user elements (e.g. 'my list', 'your account', etc.).
This commit settles on the use of 'My', but only for labels, not
for "dialog" (e.g. 'Your payment has been approved') or for
imperative statements (e.g. 'Please change your password'). One
text which is borderline is 'Log in to Your Account', but I
decided to treat it as imperative and leave it alone for now.

This commit also changes a heading on the list page which was
lacking title case, as the rest of the interface uses title
case for all headings.

Signed-off-by: Dan Wells <dbw2@calvin.edu>