Revise populate_geometry_columns and AddGeometryColumns to have optional use_typmod argument (typmod support)

[robe]

The plan for these: again a continuation of #944

1) They will no longer add/delete entries to the geometry_columns since that now reads from constraints and system catalogs

2) They will have an options use_typmod which we will default to true. Anyone wanting the old constraint behavior will have to pass in a false for second argument.

IF typmod is chosen, will create geometries using form

ALTER TABLE ... ADD COLUMN geometry(PointZ,4326) etc.

If constraint is chosen, will do as before just creating an unadorned geometry with check constraints

3) Will accept both old format name and Paul's new fangled names.

[robe]

Done at r7548