37 branching 2

[arthanson]

Fixes: #37

Removes branching from custom objects.

Will also need to add to the documentation that the following will need to be added to the configuration.py (or appended on any current PLUGINS_CONFIG:

PLUGINS_CONFIG = {
    'netbox_branching': {
        'exempt_models': [
            'netbox_custom_objects.customobjecttype',
            'netbox_custom_objects.customobjecttypefield',
        ],
    },
}

If you edit and are on a branch and have OBJECT or MULTI_OBJECT fields that point to non custom-object models you will get the following warning on the edit screen:

[arthanson]

@mrmrcoleman Please note the documentation will need to be updated with the PLUGINS_CONFIG settings.