'Add an InvSampler, and an example JO for flat field curvature and beamline IP...

'Add an InvSampler, and an example JO for flat field curvature and beamline IP sampling. Plus some more general code tweaks.' (ParticleGun-02-01-00)

	* Tagging: ParticleGun-02-01-00

	* Add an example JO showing how to use the inverse sampler to
	sample flat in B-field curvature and how to couple together
	momentum and position sampling to give an impact parameter
	distribution.

2016-04-05  Andy Buckley  <andy.buckley@cern.ch>

	* Explicitly force more sampler constructor args to float type.

	* Add InverseSampler, for e.g. B-field curvature ~ 1/pT.