Added option to make Bacula's emailing policy less verbose

Previously the only Messages resource was "Standard", which sent emails on most
events, including "Backup OK of <node>..." and the like. Renamed "Standard" as
"All" and added a new Messages resource called "AllButInformational" which does
not send any informational messages such as the one above. Message policy can be
configured on a node-by-node basis by using the new $messages parameter in
bacula::filedaemon class - see it's API for more details.

WARNING: this change will temporarily break your Bacula environment due to the
missing "Standard" Messages resource unless you do Puppet runs on all
filedaemons to update their exported Director configuration fragments before
running Puppet on the Director server.

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>