Move language.all_dictionaries to repository

[jzohrab]

This method uses the implicit db.session which is being broken as part of #503.

To change:

lute/term/routes.py:        language_dicts=Language.all_dictionaries(),

lute/models/language.py:        for lang in Language.query.all():

tests/orm/test_Language.py:    assert json.dumps(Language.all_dictionaries()) == exp

[jzohrab]

Done in develop