BUG: Use ontology terms for EBI investigation_type

Use the terms stored in the database and add a new argument, `new_investigation_type`, which is only relevant if the value passed in `investigation_type` is `Other`.

See issue #405.

NOT READY FOR MERGE - I couldn't run the tests in my system.
I am not sure I understand this comment.

On (Nov-10-14|15:17), adamrp wrote:
> > @@ -1264,8 +1264,8 @@ def validate_investigation_type(self, investigation_type):
> >          QiitaDBColumnError
> >              The investigation type is not in the ENA ontology
> >          """
> > -        investigation_types = Ontology(convert_to_id('ENA', 'ontology'))
> > -        terms = investigation_types.terms
> > +        ontology = Ontology(convert_to_id('ENA', 'ontology'))
> > +        terms = ontology.terms + ontology.user_defined_terms
> 
> Hmm okay I guess that makes sense. Just the same, it might be nice to know whether a checked term is part of the actual ontology, or part of the addenda added by users, so maybe this function should return three possible values: `"not_ontology"`, `"user_defined"`, and `"ontology"`?
> 
> ---
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> https://github.com/biocore/qiita/pull/522/files#r20121465