Upgraded to FontAwesome 4.0.3

For the sake of compatibility with WCF 2.0/FA 3.2.1, I have kept the "old" css-classes along with the new ones. There are two exceptions:
 1. The LESS-variables were unmodified and still reflect FA 3.2.1
 2. There are no "old style" class names for the bunch of new items introduced with FA 4.0