#593 Allow annotations on enumerations and enumeration literals

• Best to review per commit.
• Enumerations are declarations, and thus did not need a metamodel change. Enumeration literals did need a change.
• In CIF syntax, moved Identifiers to just before Identifier, to have them closer together, like the new AnnotatedIdentifiers/AnnotatedIdentifier.
• Last commit extends the CIF pretty printer tests for 'doc' annotations, as they also allows multiple arguments now (not strictly related to enumerations/literals).

Addresses #593