applet: make build_message() more general

For future improvements in generating of notification messages.

Related to rhbz#998066

Signed-off-by: Jakub Filak <jfilak@redhat.com>
wrap check for incomplete problem in a function

abrtd recognizes incomplete problem through absence of 'count' element.

Other application might want to do the same check and we definitely do
not want to implement it in same way as abrtd.

We should at least try to hide implementation details.

Related to rhbz#998066

Signed-off-by: Jakub Filak <jfilak@redhat.com>
applet: properly handle incomplete problems

Notify those problems only if user wishes it and show the explanatory
text in the notification bubble.

Related rhbz#998066

Signed-off-by: Jakub Filak <jfilak@redhat.com>