* Big revamp in xfconf.py
- added plugin/module_utils/module_helper.py
- scaffold class for writing modules, beyond standard AnsibleModule
- automatic capture of exceptions
- easier dependency testing
- StateMixin to easily handle different behaviours for 'state' param
- CmdMixin to easily run external commands
- adapted test_xfconf.py
- the args for run_command are now lists instead of a string
- value and previous_value were not being tested before (because xfconf wasn't filling results - see below)
- added more tests: setting value to previous_value, getting non-existent property
- rewritten xfconf module, keeping the same results
- original module posted results as ansible_facts, this version still does it for compatibility, but also adds to the module result
* Added suggestions from the PR
* Added russoz as maintainer for the module_utils/module_helper.py file
* Formatting using printf-style requires special treatment
Strings not containing substitution tokens must work as well.
* Tidied up variables in module definition
* Tests with ArgFormat and DependencyCtxMgr
* pytest parameters must be in the same order, it seems
* improved testing for the DependencyCtxMgr
* fixed test for older pythons
* Moved changed property to improve readability
* Added testcase for state: absent and adjusted xfconf after it
* Fixed param name environ_update in run_command()
* added changelog fragment
* fixed tests after run_command param change
