PDB-279 Sanitize report imports

Previously we had a bug PDB-85 that caused our exports on 1.5.x to fail. This
has been fixed, but alas people are trying to import those broken dumps into
1.6.x and finding it doesn't work.

This patch sanitizes our imports by only using select keys from the reports
model and dropping everything else.

Signed-off-by: Ken Barber <ken@bob.sh>