LArSoft

A recent change to GausHitFinder introduces an optional hit filtering algorithm.
Unfortunately, the module requires the configuration of the algorithm even if the algorithm itself is not run (which is in fact the default behaviour):

• this is a breaking change, since existing configurations have to add the filter algorithm configuration, whether they want to use it or not
• it makes no sense to have to specify a (even dummy) configuration for something that is explicitly not used

The fix is easy: just provide a default value for that configuration parameter and do not instantiate the algorithm unless it's required.