EntryCapture implementation

EntryCapture entity can be used in replacement of a Validator when
registering usable components to the blister.api.validator()

+ supersede can be validator.supersede or
entry_cature.validator.supersede
+ EntryCapture model couples Renderer and Validator

+ EntryRenderer implementing webassets pip package.
+ to_obj method on Validator accepts {} to merge in final output.
+ RenderSet.to_obj accepts a  {} to merge with
+ bister.__init__ registers the entryCapture validator