Use identical User Agents for csync and the Qt parts

Use identical User Agents for csync and the Qt parts

Also, use the mirall version for ocsync.

Currently, the csync engine part and the Qt part have different UAs,
and this makes debugging (i.e. reading access logs) difficult. On
top, we haven't increased the ocsync version number in ages. So
as a consequence, I think it would be the best to have ocsync
and the rest share the same version number, and make them identify
with the same user agent.

To ease debugging for our side, we'll still append "(csyncoC)"
for calls made by csync.