BUG: Fixing missing char type and doc for Thresholding filters

In C++ char, unsigned char, and signed char are distinct type. The
AutoMinMax IVAR for histogram based thresholds are now disabled for
char types. Also the documentation is corrected to match the code.

Change-Id: Ib4a3e47a6466980fd4f6d03e9e25baa63c8081c1
COMP: Add missing itkVerson.h header.

to itkVersorTransformOptimizerv4.h.

Change-Id: Iadd4c325a17e7c23f2f612d208e2017355b6de1d
Merge topic 'versor-header'

bb5eea30 COMP: Add missing itkVerson.h header.
Merge topic 'FixAutoThreadholdAutoMinMax'

f85a46f6 BUG: Fixing missing char type and doc for Thresholding filters