Add description on profile e-mail field

Issue Summary

There is an e-mail profile field (separate from a user's account e-mail) that is used for the Faculty and Staff pages. We need to add some descriptive text to that field to inform users that:

1. This field will be publicly visible
2. They can opt to leave this field blank if they don't want their e-mail address exposed
3. This can be different than their account e-mail (i.e. to address the, "why do I have to type my e-mail twice?" question)