The option will be passed to the Popen object created and will be used to
execute the command instead of the default shell.

 - added terse syntax to modules.rst
 - added description of special variables to template module

Add module common code to allow it to be easier to indicate whether arguments are mutually exclusive, required in conjunction, or whether one of a list of arguments is required.  This simplifies writing Python modules.

whitespace + remove deprecated YAML parser (migration script lives in examples/scripts and warning was added
in 0.6 release)

Setup module no longer saves to disk, as templates are mostly useful in playbooks and this allows lots of simplifications
around file pathing and removes occasional permissions conflicts depending on how things are used.