Mobile registration optimizations and tests (#62)

* Mobile registration optimizations

- don't autocaptialize or autocorrect on username field
- show each password field in their own row
- improve position of tooltip on mobile so that it's visible

* Use optional prop rather than default prop.

* Redirect to welcome screen if mobile_registration is requested but not enabled in the config.

* autocorrect value should be "off"

* Add unit tests for mobile registration

* Fix test typo

* Fix typo

src/components/structures/auth/Registration.tsx

@@ -627,6 +627,7 @@ export default class Registration extends React.Component<IProps, IState> {
                         serverConfig={this.props.serverConfig}
                         canSubmit={!this.state.serverErrorIsFatal}
                         matrixClient={this.state.matrixClient}
+                        mobileRegister={this.props.mobileRegister}
                     />
                 </React.Fragment>
             );
@@ -779,7 +780,11 @@ export default class Registration extends React.Component<IProps, IState> {
             );
         }
         if (this.props.mobileRegister) {
-            return <div className="mx_MobileRegister_body">{body}</div>;
+            return (
+                <div className="mx_MobileRegister_body" data-testid="mobile-register">
+                    {body}
+                </div>
+            );
         }
         return (
             <AuthPage>