MP6

MP6 has landed in trunk.

This is a great opportunity to have a real good spring clean of all the styles.

* MP6-ify the styles. Mainly new buttons & more whitespace.
* More structure. Use @import to include a stylesheet for each field.
* Remove styles that are old or duplicate. Was quite a lot of this!.
* Remove some inline styles & non-prefixed class names

I am still loading the old styles for WP pre 3.8. This allows us to merge this ASAP and those using trunk and MP6 plugin will get the benefits already. If we need to we can maintain a backwards compatable non MP6 stylesheet going forwards - we can do although it would be a pain. 

TODO
- [x] test in IE - IE8+ are all fine. IE7 doesn't really seem supported by MP6 at this point.
- [x] check backwards compatability.

Note I have merged #115 into this already. So review/merge that first.