enable tag vocabularies

[hvwaldow]

• provides the property "vocabulary", the value of which is the name of the vocabulary.
  Example:

  {
  "field_name": "systems",
  "label": "Systems",
  "preset": "multiple_select",
  "vocabulary": "systems",
  "required": true
  },

• provides the property "free_tags_only" in the top level of the schema definition. "free_tags_only": true will prevent vocabulary tags from being listed in the free tags' display.

• Currently tested with presets select and multiple_select.

[wardi]

This means vocabulary choices are expanded into the schema once on startup, so the server needs to be restarted if the vocabulary tags are modified?

[hvwaldow]

That is correct. I figure its better than talking to the database in each request.

[hvwaldow]

This is problematic on a more fundamental level because initialization of a fresh db fails upon trying to get.vocabulary_list when there are no vocabularies yet. I am closing to re-think that.