SSP-598 Output term code in EA roster selection pull-down.

Helps instructors distinguish between pull-down options when they
teach the same course/section in multiple terms.

Also tweaks option label building in general to skip delimiters
if the corresponding value (title or term) is falsy, e.g. null,
empty string, etc.
SSP-599 Add term code discriminator when looking up EA courses.

Ended up a very large patch, in large part b/c the EA model had to change,
not just the roster selection code, else EA mail couldn't be sent if
faculty taught the same course in multiple terms.
SSP-599 Fix bad Liquibase changeset ID and rollback target.
SSP-603 Add status code on external enrollment model.

Includes changes to Early Alert portlet to display the status code
after attempting to convert it to a more display-friendly name. The
name is configured with a new record in the config table that takes
a JSON string describing those code->name mappings. The default mappings
only have one mapping, which will translate a missing status code to
"Enrolled".

Removed the "Student Type" column from the EA portlet's roster view
and replaced it with the new "Status" column. Didn't see that
the student type column would ever be populated given the current APIs.