Eliminate redundant RealType math ops

We will have converters between `double` and `RealType`. Hence, `PrimitiveMath` will cover most of the necessary binary and unary operations, at least for most of the common `RealType` classes. Therefore, many of the operations in `net.imagej.ops.arithmetic.real` could be eliminated.

Start by inspecting the operations under net.imagej.ops.arithmetic.real and comparing them with the coverage provided by PrimitiveMath and the planned double/RealType converters. Inventory which binary and unary operations are redundant for common RealType classes; done means the unnecessary operations are removed without losing required support.

Written by the indexing model from the issue text.