Add get_main_logger() method to EDMCLogging.py

This is so the decision on appname versus appcmdname is in one place.

EDMCLogging.py

@@ -10,13 +10,14 @@ strings.
 import inspect
 import logging
 import logging.handlers
+import os
 import pathlib
 import tempfile
 # So that any warning about accessing a protected member is only in one place.
 from sys import _getframe as getframe
 from typing import Tuple
 
-from config import appname, config
+from config import appcmdname, appname, config
 
 # TODO: Tests:
 #
@@ -327,6 +328,17 @@ class EDMCContextFilter(logging.Filter):
         return module_name
 
 
+def get_main_logger() -> logging.Logger:
+    """Return the correct logger for how the program is being run."""
+
+    if not os.getenv("EDMC_NO_UI"):
+        # GUI app being run
+        return logging.getLogger(appname)
+    else:
+        # Must be the CLI
+        return logging.getLogger(appcmdname)
+
+
 # Singleton
 loglevel = config.get('loglevel')
 if not loglevel: