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.
Yeah, as far as I know we are not. It also seems a bit outside of the
scope of the PrepTemplate object, maybe should be something belonging to
the Ontology class? Do you have a specific use-case in mind @adamrp.

On (Nov-11-14|13:04), Antonio Gonzalez 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
> 
> Got it. I think it will be nice to have if we were actually using it but we are not at this point, right? 
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/biocore/qiita/pull/522/files#r20180170