postgres provider changes:
- ignore infinite filter rectangles
- also disconnect selection connection if no supported layers were found
datum transformations:
- copy descriptions, preference and deprecation from GDAL
- remember position of dialog
- allow hiding of deprecated transformations

SQL:
ALTER TABLE tbl_datum_transform ADD remarks varchar;
ALTER TABLE tbl_datum_transform ADD scope varchar;
ALTER TABLE tbl_datum_transform ADD preferred boolean;
ALTER TABLE tbl_datum_transform ADD deprecated boolean;
ALTER TABLE tbl_datum_transform ADD area_of_use_code varchar;