modularization of inventory_import command

This separates file parsing logic that was mixed
in with other important code inside of the
inventory import command.

The logic around MemObject data structures was
moved to utils, and the file parsing was moved
to a legacy module. As of this commit, that
module can operate within the Tower environment
but it will be removed.

Also refactor the loggers to fix old bug and
work inside of the different contexts - the
Loader classes, mem objects, and hopefully
the inventory modules eventually.

pytest.ini

@@ -8,3 +8,5 @@ markers =
     ac: access control test
     license_feature: ensure license features are accessible or not depending on license
     mongo_db: drop mongodb test database before test runs
+    survey: tests related to survey feature
+    inventory_import: tests of code used by inventory import command