Verbosity system

[jClugstor]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

This is the start of the verbosity system as described in #962.

This is at a point where the SciMLMessage macro works and I can set the log level settings of any message.

I still need to add individual options for every verbosity group. This just includes ODEVerbosity, NonlinearVerbosity, LinearVerbosity right now as those will be the three needed for OrdinaryDiffEq.

To-Do:

• Add individual options to all of the verbosity groups
• Flesh out the docs page and add to the docs, add more examples etc.
• Add a custom default logger to make filtering and printing to file easy for users