STYLE: logical ops return bool (issue #1043)

- these currently only with bool parameters, but the return value should
  nonetheless always be a bool value:

      andOp(), orOp(), lessOp(), lessEqOp(), greaterOp(), greaterEqOp()

- renamed the unused eqEqOp() to equalOp() for naming consistency with
  the equal() global function.

ENH: equalOp() specialization for scalars

- function object version of the equal() function.
  The default constructor uses the same tolerance (VSMALL),
  but can also supply an alternative tolerance on construction.