README: Use 'dora' as adviced branch

Change-Id: If0e9e7409477663cf02ff1f4a1b08ce9fb20e813
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
default.xml: Remove default revision

We ought to make it explicit so we always have a clear idea
where we're getting the source from.

Change-Id: I253adb5ed467c3577e5408fd68c1461841f3ed70
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>