service-management: use virtual functions
systemd-syslog: auto migrate from unix-stream("/dev/log") to systemd-syslog source
when systemd is used
service-management: fix always using of dummy service management
system-source: Use systemd-journal() if appropriate

If running under systemd, use the systemd journal instead of the
forwarding socket.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #243 from algernon/f/3.6/system-source/systemd-journal

system-source: Use systemd-journal() if appropriate
system-source: Allow messages to flow through JSON

In case a message does not match the JSON marker, allow them to flow
through unmodified. This makes system() work with non-CIM messages
again.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Merge pull request #245 from algernon/f/3.6/system-source/json-channels

system-source: Allow messages to flow through JSON
Merge pull request #236 from ihrwein/f/systemd-syslog-source-refactor

F/systemd syslog source refactor