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
Merge pull request #25 from ahoenselaar/future

Fix selection of dependent tuples in dj.BaseRelvar.del()
Don't isolate strict projections in dj.GeneralRelvar.makeWhereCause
Forward dj.GeneralRelvar.view() arguments to fetch()

Allows for the application of ORDER BY or LIMIT before displaying data
Merge branch 'experiment' into future

Conflicts:
	+dj/BaseRelvar.m
	+dj/GeneralRelvar.m
fixed bug that affected ERD when some of the schemas were not yet loaded.