consider moving plugin validation to BasePlugin constructor

[chris48s]

At the moment, there's a stand-alone validatePlugin() method which is called on each plugin as v8r loads them. Would it make more sense to move that to BasePlugin.constructor() ? I think that would improve the process of developing plugins that live in their own repo as you can easily ensure your plugin passes validation checks in the plugin's test suite.

[chris48s]

A possible problem with this would be that plugins could override the validation, which would be bad.