[general] Fix repo urls to match new ssu features.

Signed-off-by: Marko Saukko <marko.saukko@jollamobile.com>
[ssu.ini] Make latest the default release.

Signed-off-by: Marko Saukko <marko.saukko@jollamobile.com>
Cleanup the default values.

This is safe to do as ssu haven't been used in nemo yet so no need to worry about compatibility yet.

Signed-off-by: Marko Saukko <marko.saukko@jollamobile.com>