Change default "contact form" email address from brigade-info@ CfA email

We just got an email from someone who used [the "Contact Us" page](https://codeforcroatia.org/contact) on the codeforcroatia.org instance of Laddr. It happened to be spam, but that led me to investigate how we got it, and I noticed that the default email address for the contact form is brigade-info@. This strikes me as almost certainly not the place you want to send users, since they're not going to get a response from the right people.

Not sure what the right fix is -- consider changing it to a value that must be configured? Or disable the page if the value is not provided?