fixes #6820 - apipie-bindings should enforce required params, BZ 1116803
adding function on actions and params to build trees of their params
adding deep recursive validation of params
removing reliance on gettext for internationalization
refs #6820 - refactoring Param#tree and Action#api_params_tree
refs #6820 - adding deep diffing of required_params vs passed params
wip
wip
wip3