Revert "Remove backref to owner since it seems to be unused, but it crashed attempts to remove items which have been removed from static data"

This reverts commit 8ee900a90e.

eos/db/saveddata/fit.py

@@ -191,6 +191,7 @@ mapper(es_Fit, fits_table,
                    Booster,
                    collection_class=HandledBoosterList,
                    cascade='all, delete, delete-orphan',
+                   backref='owner',
                    single_parent=True),
            "_Fit__drones": relation(
                    Drone,
@@ -226,6 +227,7 @@ mapper(es_Fit, fits_table,
                    Implant,
                    collection_class=HandledImplantList,
                    cascade='all, delete, delete-orphan',
+                   backref='owner',
                    single_parent=True,
                    primaryjoin=fitImplants_table.c.fitID == fits_table.c.ID,
                    secondaryjoin=fitImplants_table.c.implantID == Implant.ID,