IE fixes

Still working through a few things...
General CSS fixes for all browsers

A number of CSS fixes.

All IE
- Created an all IE css file and including it inside IE 6,7,8 files
- Fix for white area around radios and check boxes

IE7
- Few fixes due to known bugs in IE 7

All Browsers
- Using a inline level element to wrap block level elements
- Setting span.block-label to block level element.
- No visible differance in browsers apart from IE 7
Major changes to Form:
- Form.attributes is gone. Replaced by Form.attribute, which takes
  the attribute name and the type user input should be cooerced to.
  Fixes #333.
- Abandon ActiveModel interface for `#initialize`. Forms now take
  a model instance as the only argument. We didn't use the AM
  interface anywhere in the code and made it possible for Forms
  to be incorrectly initialized, i.e. without a model instance.
- Promote `#target` to public method in all Form subclasses, it
  shouldn't have been private anyway.
Merge pull request #336 from ministryofjustice/enhancement/virtus

Replace custom form implementation with Virtus (WIP)
Merge pull request #340 from ministryofjustice/fixes/ie-related

Fixes/ie related
front-end/sign-out

updated copy and layout as per noteable
Updated tests

..to reflect copy changes
fixed broken test and updated page to reflect design in notable
reverted save_and_open_page in rails helper
Merge pull request #316 from ministryofjustice/front-end/sign-out

front-end/sign-out
consolidated and moved some IE fixes around.
Merge pull request #346 from ministryofjustice/fixes/ie

consolidated and moved some IE fixes around.
fixes #341
simplifed remove JS