Make __version__ global available for all supported python versions

Extract the version information from the packaging and set it as version global. For the still supported python 3.7 this also handles the installation of the importlib-metadata package.

map/__init__.py

 """ My Awesome Package """
+
+try:
+    from importlib import metadata
+except ImportError:  # for Python<3.8
+    import importlib_metadata as metadata
+
+__version__ = metadata.version("my-awseome-app")