Get a specific vocabulary details.
opal.vocabulary(opal, taxonomy, vocabulary)Opal object.
Name of the taxonomy
Name of the vocabulary in the taxonomy
Other taxonomy functions: 
opal.taxonomies(),
opal.taxonomy_delete(),
opal.taxonomy_download(),
opal.taxonomy_upload(),
opal.taxonomy(),
opal.terms(),
opal.vocabularies()
if (FALSE) {
o <- opal.login('administrator','password', url='https://opal-demo.obiba.org')
opal.vocabulary(o, 'Mlstr_area', 'Lifestyle_behaviours')
opal.logout(o)
}