* add checking of interfaces, providing defaults or errors if required keys are not defined
* fix so that iteration of interfaces only happens if defined
* Update zabbix_host documentation (extend ipmi_-documentation, and update style to be consistent on the rest while we are at it)
* Remove ipmi_parameters being added to the API call when not required
* remove optional parameters from add_host, as well
* reorder interfaces handling for force=no, making sure it works when no interfaces are specified in the module parameters
when no interfaces are specified on update, use existing interfaces obtained from API.
check whether visible_name is set in check_all_properties; if not set as module parameter, no comparison is necessary.
Check if description is set as module parameter before comparing as well
* link_templates need the same treatment
* add inventory update checks and simplify update procedure
* make specifying proxy optional on update (keeping it as is when not specified), as well
* pep8 fixes
* add tls_*-checks for updates and make tls_*-options actually optional
