SSP-2681 Fix up 2.4/2.5 DDL

Addresses a few problems:

  - stg_external_catalog_year.name should be 100 wide, was 50
  - stg_external_catalog_year PK should be code, was code+name
  - stg_external_substitutable_course.catalog_year_code missing
  - stg_external_substitutable_course 2.4 DDL had PK and uq constraint
  - unbalanced SET ANSI_PADDING ON
  - 2.4 tables not highlighted in SQLServer drop DDL