[DEV] Use geofabrik .json for countries and regions for internal processing (from former `constants.py` and `wahoomc/resources/json`)

[treee111]

This PR…

• gets rid of the locally defined countries, continents (regions) and country to geofabrik + county to continents mapping for wahoomc internal processing
• accesses the at all time downloaded geofabrik .json file for these types of checks via a own wahoomc/geofabrik_json.py file and class

Considerations and implementations

This PR takes away local hardcoded values in constants.py and wahoomc/resources/json/ by using fresh downloaded geofabrik .json therefore. This ensures

• up-to-date constants
• less translation calls (country to geofabrik country etc.)
• dismantling of workarounds
• better readable code

and most important:

• makes the ways possible to fully get away from wahoomc/resources/json/ files with the next PR #182

The local wahoomc/resources/json/ files are still there and the -co as well as -xy coding uses it. The reason is that X/Y processing at the time of writing is not integrated using geofabrik .json. For comparison of local json/ and geofabrik .json output, the files are still there for now. In the next PR, all that will be done.

How to test

1. do usual tests
2. run unittests

Pull Request Checklist

• [x] Reviewed the Contributing Guidelines
  • Especially the Pull-Requests section
• [x] Commits (and commit-messages) are understandable
• [x] Tested with macOS / Linux
• [x] Tested with Windows