Fix/384 - Move IE Support to "Compatibility" Namespace

Two items in the new Compatibility namespace:

* `Compatibility/Image/Scaling` adds a filter for bicubic scaling on all images in IE7 and below, to deal with the atrocious level of support provided by IE 7 and below for scaling.
* `Compatibility/CSS/Filter/Border_Radius` adds `Blocks.IE.css.filter.borderRadius()` method that allows one to transparently generate a wrapper class for dealing with the filter + border-radius bug in IE (where the filter overrides the radius). This means that one does not need to put a wrapper in the markup (used by `nav.bar`).