[securedrop-log] Consider splitting securedrop-log into 2 distinct packages

[emkll]

In order to make make the provisioning and logging configuration easier, we should strongly consider splitting the log package into 2 distinct components:

1. log-server: receives, processes and writes received logs to disk
2. log-forwarder: sends logs to sd-log

It seems like, as a compromise, we could address this is packaging only, shipping only the configuration-specific changes required for sending or receiving logs, while using the same securedrop-log tarball

[kushaldas]

I would suggest to split the source into two different projects, so that it becomes much easier to do the packaging.