Feature/version comparator

Hey guys,

this is a UI to support comparing versions of a page. It indicates things like property changed/added/removed, resource added/removed etc. 

There is still some brushing/documenting/writing tests necessary but I would like to get some initial feedback before doing so.

It can be easily tested by navigating to: http://localhost:4502/etc/acs-commons/versioncompare.html?path=/content/geometrixx/de/products/jcr:content
Before doing so, make sure you create a few versions with changes for the page under /content/geometrixx/de/products

Thanks,
Steffen
`StringUtils.startsWithAny(key, ignoredProperties)` would be a bit cleaner