[FEATURE] stdWrap for Assets

I'd like to contribute the stdWrap functionality for any asset content.

The specific use case for me was adding dynamic pixel-tracking javascript files (like Google Analytics or Omniture) that depend on accessing system values like getIndpEnv:TYPO3_HOST_ONLY or specific userFunc's to have the content be dynamic. I think there are a lot more use cases where it makes sense to generate the javascript dynamically, while still having it use the enhanced dependency management that VHS offers.

I'd be willing to add unit tests for this as well. My first intention is to get feedback if this functionality, in the current or modified form, is of interest to you.

Example using TypoScript.
https://gist.github.com/efrister/6792430

Example using the ViewHelper.
https://gist.github.com/efrister/6792420