check pi_name content

[tcarval]

The PI_NAME variable should be tested againt the vocabulary table R40
This is a follow-on of OneArgo/ArgoVocabs#6

[delphinedobler]

Alert level: warning; this should be implemented in the 2.9.5 release to come.

[YvanEuroArgo]

implemented since https://github.com/OneArgo/ArgoFormatChecker/releases/tag/v3.0.0