Import all namespaces defined in namaspaces.py into db_utils.py

[bgajdero]

Update processing of ontology_cache to import all (import *) for all paths added to owlready2.onto_path.

The final result should be that any namespaces defined in all namespaces.py files are imported and accessible to db_utils.db.

Assume that what ever path is added to onto_path, in the same directory as cache_ontology, there is a file name namespaces.py. The variables defined in this file should be imported.

For example, here, the path input/ontology_cache/ is added. This can then be referenced in db_utils as `from .input.namespaces.