Adding CssUrlAuthorizationProcessor

Interactions between multiple processors can 'break' URLs that are known
to the ResourceAuthorizationManager. This processor can be put as a post
processor following the other processors to 'fix' this.
Changing CssUrlAuthorizationProcessor to extend CssUrlRewritingProcessor
Merge pull request #185 from nla/1.7.x

Adding CssUrlAuthorizationProcessor post processor
fix failing test
Merge branch 'issue879' into 1.7.x