fix haproxy config if webapp and mx run on the same host

the problem was, that both site_mx::haproxy and site_webapp::haproxy
declared the same resource.
I fixed it by moving that resource to site_haproxy.
Since that gets included by both classes, everything works like
a charm
remove old classes

site_mx::haproxy and site_webapp::haproxy only
included site_haproxy. They didn't do anything else.
So just include site_haproxy in manifests/init.pp and
remove the unused classes
remove unused variable local_ports
move haproxy-template to modules/site_haproxy
Merge remote-tracking branch 'cz8s/feature/allow_webapp_and_mx_on_one_host' into develop