LP#1228392 Allow mapped fields to show up in reporter template builder

LP#1228392 Allow mapped fields to show up in reporter template builder

Since inception, mapped fields have been hidden in the reporter, the
logic being that showing them shows too much (in particular, a circular
reference back to ourselves), and is therefore confusing.

However, not showing them means we have two options:
1) Don't use those fields in the reporter.
2) Add a second, non-mapped field just for the reporter.

These options both seem less than ideal, so for now, just let them
show up, and let the user sort it out.

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