Add logging plugins

[edvgui]

This module has the std::print module, which works well when compiling a model by hand, but very poorly when using the project fixture of pytest_inmanta.

The idea is to offer another interface for the user to "print out" information from the model, based on python logging.

Open questions:

1. It can either be a single plugin, similar to logging.Logger.log, or multiple plugins, for the different log levels?
2. Keep the python logging interface, or the agent logging interface (keyword parameters are better there)?

[bartv]

I think it makes sense in general to be able to add logging to the model. I am going to create another ticket to actually handle the project fixture not showing stdout on failure