Updates the look and feel of the two (experimental and disabled by
default) links to student records.
Also converts the 'student_records' waffle switch to a waffle flag
named 'credentials.student_records.
LEARNER-5246
Add some waffle-guarded connection points to the Credentials service
to start filling out the user flow for Student Records.
Specifically, add a button to the Program Progress Details page if
a certificate exists, and add a link in the Learner Profile page.
Both only appear if the 'student_records' waffle switch is active.
LEARNER-4701
