Implement simple team-based registration (#620)

* Implement simple team-based registration

Config required goes in the `teams` top-level property in config.json. This consists of an array of team objects:
```json
{
  "name": "University of Bath",
  "emailSuffix": "bath.ac.uk"
}
```
These can be selected on registration and require a user to have a certain email address in order to register as part of a team. This is for vector-im/riot-web#2940. The next step would be sending users with emails matching the emailSuffix of a team to the correct welcome page as in vector-im/riot-web#2430.

src/components/structures/MatrixChat.js

@@ -1003,6 +1003,7 @@ module.exports = React.createClass({
                     defaultHsUrl={this.getDefaultHsUrl()}
                     defaultIsUrl={this.getDefaultIsUrl()}
                     brand={this.props.config.brand}
+                    teamsConfig={this.props.config.teamsConfig}
                     customHsUrl={this.getCurrentHsUrl()}
                     customIsUrl={this.getCurrentIsUrl()}
                     registrationUrl={this.props.registrationUrl}