Clean up and move pekko.conf

[sebastian-peter]

A bunch of settings are probably not needed anymore:

• pekko.remote because we do not use the network
• coordinated-shutdown might be obsolete because we wait for results to be flushed out ourselves (ResultListener)

Furthermore, to make the configuration apply per default, it can be moved to src/main/resources/application.conf.
This means it does not have to be linked by the simona config (e.g. vn_simona.conf) anymore.