- change the behaviour of the ringwelcomeview to display the Ring
username when available.

- change the label of the QR code button to "Ring ID QR code" to avoid
confusion when displaying the username. The QR code is not a QR code for
the username but always for the Ring ID.

- make the label of the QR code button translatable. Even if its only a
couple non-translatable words, some languages have different word orders
or whatever...

Tuleap: #681
Change-Id: Ic4ddfae34bbc7120d94e2c6ef7e8f323f8cecef6