Fix dj.assert statement in dj.Schema.erd
Fix selection of dependent tuples in dj.BaseRelvar.del()

* When deleting tuples from a parent table, all affected subtables
  from dependentent tables also have to be deleted.
* The dependency relationship is based on the primary key fields
  of the parent table.
* When restricting dependent RelVars in del(), the restricting
  RelVar has to be projected onto its set of primary key fields.
* Otherwise, some dependent tuples will be missed and the del()
  operation will fail at the level of MySQL
Don't isolate strict projections in dj.GeneralRelvar.makeWhereCause

Conflicts:
	+dj/GeneralRelvar.m
Forward dj.GeneralRelvar.view() arguments to fetch()

Allows for the application of ORDER BY or LIMIT before displaying data

Conflicts:
	+dj/GeneralRelvar.m
Restore return value of dj.GeneralRelvar.view()