Improve performance of heavily used BFieldCache::getB method by moving...

Improve performance of heavily used BFieldCache::getB method by moving short->float type conversions out of tight for-loop. New BFieldCache::getB method is about 1.4 times faster. Bit-wise identical output is guaranteed (MagFieldServices-00-01-36)

	* Improve performance of heavily used BFieldCache::getB method by moving
	short->float type conversions out of tight for-loop. New BFieldCache::getB
	method is about 1.4 times faster.
		* Bit-wise identical output is guaranteed
	* Tagging as MagFieldServices-00-01-36


Former-commit-id: 300d7852