Support CEN/CENELEC identifiers for all document types

[ronaldtse]

From https://experts.cen.eu/media/Experts/cen-clc_projex-online_user-guide.pdf

• EN
• HD
• CWA
• TS
• TR
• CG (CEN Guide)

All these documents, except CG can be created with an Amendment / Corrigendum.

[mico]

Another source for document types: https://www.cencenelec.eu/european-standardization/european-standards/types-of-deliverables/

[ronaldtse]

Only CWA and HD added in #12, reopening for the rest.

[ronaldtse]

Actually they are all supported now. We just don't have enough specs for "CEN Guide".