Resolve <recompute_regularization_interval> differences

[akenmorris]

itkParticleMeshBasedGeneralEntropyGradientFunction and itkParticleEnsembleEntropyFunction use this parameter in very different ways and it needs to be reconciled.

[sheryjoe]

[ ] check/update use cases with recompute = 1 [ ] change to recompute_covariance_interval, regularization should be updated before computing covariance.

[akenmorris]

This should be fairly easy to do, but it's just going to be very time consuming to re-verify all of the use cases. Let's put it off for 6.3 and I believe it should be easier to do if #1063 is done first.

[cchriste]

itkParticleMeshBasedGeneralEntropyGradientFunction and itkParticleEnsembleEntropyFunction

Seems like they're just putting together a bunch of random words and calling it a class nowadays.