model: Replaced deprecated relation() by relationship()
model/club: Moved relationships next to the foreign keys
controllers/clubs: Fixed pilots ordering
model/tracking: Removed unnecessary primaryjoin parameter
model/club: Import cleanup
model/tracking: Removed unnecessary ForeignKey use_alter parameters

There is no circular dependency here that would justify the use
of use_alter=True.
model: Added proper ON DELETE actions to foreign key columns
model/traces: Added missing ON DELETE constraint to database
model: Removed unnecessary cascade parameters

The Postgres database will take care of cascading deletion through the
ON DELETE handlers. There is no need for SQLAlchemy to interfere.
Merge pull request #42 from Turbo87/relationships

Model relationship improvements