Add contact form to the portal

[mitar]

Probably somewhere in the footer should be a link to the contact form where users could contact administrators.

There should also be a notice that for bug reports and other issues they should use GitHub and link to the form for new GitHub issues. Of course, somewhere it could be also mentioned that it is developed as open source project and voluntarily, so they are also invited to help. (Could be through a link to about page, #243.)