This introduces three new compatibility functions for working with fields

cross-Django:

get_field_is_relation()
get_field_is_many_to_many()
get_remote_field_related_model()

It also updates several other field-relation functions to provide more

consistent results for different fiels and relation types.
Unit tests were added for most functions in this module to help catch

inconsistencies in behavior across versions of Django.

Unit tests pass on all supported versions of Django.
Used the new behavior in some in-progress changes.