Separate the logging module to avoid transitive dependencies

[eperinan]

After the version 0.6.2, log4s was added as a wrapper for the logging module.

After this adding, we are importing transitively two dependencies, log4sand journal.

This would be inconvenient for someone who only wants to use log4s for example and doesn't want to have in the classpath the dependencies from journal.

For this reason, I propose to separate the logging module into three modules.

The first module with sloggingfor JS and the algebras.
The second module for journal whose depends on the first module
The third module for log4s whose depends on the first module as well

Thoughts?