Bring specific metadata normalization back from metanorm

[aperrin66]

All the specific metanorm normalizers (i.e. those which for a specific URL or entry ID) need to be brought back into the harvesting repository.

Steps:

• move one normalizer as well as the utility functions: Update CMEMS provider #146
• move the rest of the normalizers gradually
• make metanorm properly generic, meaning it should support well known standards (CF, etc.)