New plugin for Views argument validators

It is really cool that it is possible to use Rules components to run argument (contextual filter value) validators in Views, but it is quite silly that it is such a mess setting them up. It would be nice to have a new component plugin type that automatically gets the required parameters and provided variables.

And while you're at it – load the until-then defined arguments as a list and send as an extra parameter + provided to the component.

Check out the RulesRuleSet class in includes/rules.plugins.inc for a starting point.