Processor interface missing fields

The definition for Processor, seems to be missing several of the fields described in the documentation for Package#processor. Also, I think the $process method should be listed as optional.

import {Package} from 'dgeni';

export default new Package('example')
  .processor({name: 'works', $process() {}})

  .processor({name: 'does-not-work'})

  .processor({name: 'also-does-not-work', $process() {}, $runBefore: ['works']})

  .processor({name: 'still-does-not-work', $process() {}, $runAfter: ['works']})
;

I would be happy to submit a PR for this issue if that would be helpful.

[petebacondarwin]

Done 😃

[dherges]

Yes!

Have a good night!