Add maxLength to JSON schema for dashboard title
Add maxLength to JSON schema for dashboard title

Django models require that strings have a maximum length that is a
positive integer, so let's do that now.

keithiopia/spotlight,alphagov/spotlight,alphagov/spotlight,alphagov/spotlight,keithiopia/spotlight,tijmenb/spotlight,tijmenb/spotlight,keithiopia/spotlight,tijmenb/spotlight