Implement supports for field operations with complex types

[alexgarzao]

For all complex numeric go types (see list below), the following validations must be implemented:

• eqfield
• neqfield
• gtefield
• gtfield
• ltefield
• ltfield

Go types

• complex64 the set of all complex numbers with float32 real and imaginary parts
• complex128 the set of all complex numbers with float64 real and imaginary parts