new deco method to decorate bag data; returns the data (not the bag) from sub method.
withTrait to deco messages for message/error.
test simple View response.
set error status when returning a view response with error.
eliminate all static access to the App instance.
not to set $request at the app construction.
tested view with error. set default error view in Responder; also refactored how to handle data for templates from bags.
removed code about parent, which is seemingly not necessary.
route '/view', was not necessary to test onView method.