Title search: a few improvements

[lpalbou]

Related to our discussion on Monday:

• since the minerva API doesn't allow the search of a title with multiple keywords, the field in ART should only accept a single value (currently accept multiple values as badges, but only the first value is used for the search)

• always add "gomodel:" to a model id if the user doesn't input it. The rationale is gomodel:xxx is a CURIE, which resolves to model.geneontology.org/xxx . So gomodel: should always be present in the model id. If not, that should be fixed in the repository

• last time, I try to search for a model and there was 0 result. This was correctly shown in the "Result" box, but ART was still showing the default list of models. When there is 0 result, ART should display 0 models

@vanaukenk @ukemi