Fix internet_id and uid_based_id confusion in syntax definition

I’ve added a note to indicate GUID is a synonym of UUID, and also fixed that first sentence. Thanks for the careful checking.

and another one: the https://specifications.openehr.org/releases/BASE/latest/base_types.html#_hierarchical_identifiers

suggests HIER_OBJECT_ID are mostly OIDs, but in https://specifications.openehr.org/releases/RM/latest/common.html we change that recomendation or style to GUID - of which, btw would be nice to also use the UUID.

if we don’t want to modify all docs using GUID, is it perhaps cleaner to introduce formally the GUID class (as an alias of UUID) ?

one more small issue in https://specifications.openehr.org/releases/BASE/latest/base_types.html#_identifying_versions_within_openehr_versioned_containers

The requirements on the third part of the identifier are that it be unique per system, and that it be easy to obtain or generate. It is also helpful if it is a meaningful identifier. 

I guess it is the second identifier (i.e. creating_system_id).

The syntax for internet_id was there, but I’ve improved the syntax following your comments, and re-ordered it to make it clearer.

I just notice a small related issue:

• https://specifications.openehr.org/releases/BASE/latest/base_types.html#_primitive_identifiers tells about e subtypes of UID, but grammar refers to just 2 (guid, iso_oid) omitting internet_id

• text often refers to uuid, but grammar used (alias) guid - perhaps should stick to 'uuid' in grammar as well, it will make things clear

• https://specifications.openehr.org/releases/BASE/latest/base_types.html#_identifying_versions_within_openehr_versioned_containers refers to creating system_id as reverse domain identifier, but grammar is not allowing that anymore (I assume internet_id was removed)

In the grammar, adding internet_id to uid and renaming guid to uuid might solve things.