Add documentation for capacity factors

Also reword the distribution mode documentation a bit, and move the
grouping API to the distribution mode section.
ISPN-3740 AbstractCacheTest.getDefaultClusteredCacheConfig() should not disable state transfer
ISPN-3757 Update user documentation to refer to Infinispan 6.0 javadocs

Also replace some old references to http://java.sun.com which are now redirected to http://docs.oracle.com
ISPN-3757 Fix links to old javadocs
ISPN-3752 capacityFactor is not effective

Use correct capacityFactor from joiner.
ISPN-3752 capacityFactor is not effective

* Add a functional test for capacity factors
* Copy the capacityFactor in HashConfigurationBuilder.read()