Add logging to Konstraint output

[jalseth]

This adds logging output to Konstraint as it processes policies. Debug level is used only for more verbose output, Info is used when Konstraint takes non-default paths due to user configuration as well as status updates for major steps, and Warn is used when Konstraint takes non-default paths due to implicit configurations that the user may not be aware of.

Fixes #170

Examples:

$ ./build/konstraint --log-level info doc examples -o examples/policies.md --no-rego
INFO[0000] no-rego flag is set. policy source will not be included in the documentation 
WARN[0000] no kind matchers set, this can lead to poor policy performance  name=RequiredLabels src=examples/required-labels/src.rego
INFO[0000] completed successfully                        num_policies=23

$ ./build/konstraint create examples                  
WARN[0000] skipping constraint generation due to use of parameters  name=RequiredLabels src=examples/required-labels/src.rego
INFO[0000] completed successfully                        num_policies=20

[jpreese]

LGTM, have a highly opinionated thought:

I would make all logging on by default (Info and Warn) which would mean also removing the --log-level flag and Debug outputs. I tend to go for the simple case first, and if we find a reason to require debugging, add it in a future release.

[jalseth]

Usually I prefer giving users flexibility... but I cannot imagine an actual use case for what the debug logs are currently doing so I removed them as it simplifies the PR quite a bit.