Complex-Math: Handle Operations with Scalars

First feature from @BeyondEspresso 's pull #597.

Updated the complex-math library in the radiation-plugin to handle all basic calculations (+,-,*,/) and assignment from scalars.
please remove `Complex_T(rhs.real/(rhs.real*rhs.real+rhs.imaginary*rhs.imaginary), ...`and use `lhs * (1.0/rhs)` instead to avoid code duplication.