Implement/expose simplex method to compute orientation matrix **UB**

[prjemian]

Implement (expose) the libhkl simplex method to refine the orientation matrix UB. As described in #40 (comment),

The case of computing UB with more than 2 reflections is described in the libhkl documentation (simplex computation with more than 2 reflections using the GSL library) but not yet supported in the hklpy code. This code should be revised as the simplex technique is supported in hklpy.

[prjemian]

Already implemented as method affine():

hklpy/hkl/sample.py

Lines 377 to 381 in 360609e

	def affine(self):
	"""
	Make the sample transform affine
	"""
	return self._sample.affine()