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.
That is chcked in the if statement above; the function just returns without doing anything.

Yoshiki Vázquez-Baeza

> On Nov 7, 2014, at 3:05 PM, Daniel McDonald <notifications@github.com> wrote:
> 
> In qiita_db/ontology.py:
> 
> > +    def add_user_defined_term(self, term):
> > +        """Add a user defined term to the ontology
> > +
> > +        Parameters
> > +        ----------
> > +        term : str
> > +            New user defined term to add into a given ontology
> > +        """
> > +
> > +        # we don't need to add an existing term
> > +        terms = self.user_defined_terms
> > +        if term in terms:
> > +            return
> > +
> > +        conn_handler = SQLConnectionHandler()
> > +        sql = """INSERT INTO qiita.term
> What happens if the term already exists or is that assured to not be possible?
> 
> —
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