#2867 need routines for complex_real_part and complex_imaginary_part

[Jeremy Faden]

I had a bug which was caused by code which pulled out just the real component of a complex vector, using

Ey_fourier[1:fft_size_half,0]

This ends up being quite different in function from

Ey_fourier[1:fft_size_half]

though it's only different by 2 characters (,0). There need to be routines to explicitly pull out just the real part.

[Jeremy Faden]

realPart(Ey_fourier[1:fft_size_half]) is now available.