Fixes a problem where cv attriube not were cleared

When a ContentVersion object was updated the contentVersionAttribute cache
was not cleared in the CMS app
System redirects are now created on NiceURI change

When a SiteNode is published with a change NiceURI a system redirect is
created (from the old address to the new).
Merge pull request #92 from stenbacka/sys-redirect-on-niceUriChange

Sys redirect on nice uri change