Advanced select / dropdowns

I have added support for better select / dropdown boxes using [select2.js](https://github.com/ivaynberg/select2.git) as well as a "Tag List" feature using [jQuery Tags Input](https://github.com/xoxco/jQuery-Tags-Input.git)

This adds more possibilities when adding meta (like typing text and filtering etc.)
This is a simple/basic implementation not using many features of the included libraries.

I started with this for a personal project and thought it might be useful for others as well.

I don't know if there's a policy on using external libraries. If so, and this doesn't comply, sorry. :)

Regarding licensing (I am not well versed in licensing terms):
* select2 uses [Apache License, Version 2.0](https://github.com/ivaynberg/select2/blob/master/LICENSE). This is being used legitimately I believe.
* jQuery Tags Input provides no license. I'm not sure if it's OK to be used here in that case then?

Looking forward to your feedback!