Add proper logging support

[rosalogia]

Summary

We should use a strong logging library that provides us with the ability to hide log messages with log levels at the very least. Maybe logs?

Relevant Documentation and Links

• logs opam page
• logs documentation

[oteku]

If pollinate remain a library, logging system must be a dependency injected at by the project which use pollinate.
Meaning it would be the purpose of deku to provide you a logging system that fit your expected interface (which is easy for loging)

This is usually achieved in OCaml using functors or virtual library