New trust management module

There is a new trust management module placed in the plugins folder:
plugins/modules/trust.py
The trust module allows to ensure presence and absence of trusts.

Here is the documentation for the module:
README-trust.md

New example playbooks have been added:
playbooks/trust/add-trust.yml
playbooks/trust/del-trust.yml
New tests added for the module:
tests/hbacrule/test_trust.yml