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.
In my example I removed the type cast because if the result complex number is `Complex_T<float>` we cast to double than to float and nobody knows if we had an float under or overflow.