Fixed wrapping columns at DDL script with ampersand

Instead of ampersand columns names are wrapped with double quote now.
Added schema select at RE, fixed RE after refactoring for GC

Selecting schema when database contains more that one added into RE dialog.
Fixed RE of model after previous refactor commits.
Fixed getting column constraints from certain schema at server reeng

Fixed schema "public" changed to be dynamiclly filled at `getConstraintColumns`
method.