CLC-2427 Separate grade transcript query from enrollments query

https://jira.media.berkeley.edu/jira/browse/CLC-2427

This splits the very expensive transcript search (needed for historical information in My Academics) out from the feed needed by the Dashboard widgets.

Probable next steps include:

1. Get DBA help to force use of the proper indexes on the join of enrollment records and course information. (This may be tough with a variable number of term clauses.)
2. Make the Dashboard feeds pull enrollment records only from current terms, rather than pulling enrollment records for all the terms shown by My Academics.
3. Ask the DBAs about indexing the transcript data by student LDAP ID.