Migrate to another logging library

[ninovanhooff]

We currently use Napier, which has a few issues

• Weird naming humor ("Antilog", what is that?)
• recently intrduced a crash which required all our template projects to be fixed
• Required a workaround to prevent all logging to be grouped under a single issue in Crashlytics Fix/crashlytics groups Napier error messages #76
• Seems abandoned by it's sole developer

Candidates for replacememt should be compatible with KMP. Kermit by Touchlab seems to be agood candidate.

While we are at it, it might be nice to abstract logging away by creating a global object Logger in its own module, which can be used from wherever (even without dependency injection). That would make switching logging libraries easy without touching all the usages.