[imp] proposed JPlugin changes

Better code than words :D

This includes the `getLayoutData()`  method I told you before. It allows to forget about dealing with some layout data (in this case it only adds the plugin parameters but for fields, for example, the same concept saves devs a lot of code).

I also removed some code from the constructor and moved it to a `getDefaultRenderer()`. As it can be overriden I think we can skip passing the `$options['path']` (that was wrong because it should use `$config['options']` ).

I used the vote plugin as demo.