Make HstConfigurationAugmenter more robust against recursion

The HstConfigurationAugmenter is currently very error prone for recursion, as typically the augmenters are invoked from HstManager#getVirtualhosts which can be called again from the augmenters as they get a HstManager instance.

Deprecate the augment method using the HstManager as argument and add a new method that accepts MutableVirtualhosts as an argument instead.