check naming of sentinel-2 tile

[dicaearchus]

in 'checking' 'naming' there is no function yet to check a string, if it is a correct sentinel-2 granule code or a correct datastrip code. Hence functions like:

def check_sen2_granule_code(code_str):
def check_sen2_datastrip_code(code_str):

Would be nice

[dicaearchus]

see also: https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/naming-convention