BUG:  Need to explicitly specify spline order.

This patch addresses a couple issues:
1) The spline order needed to be explicitly specified
in the B-spline reconstruction.  Since most people use
the default spline order = 3, this won't have much of
an effect but it's a bug that needed to be fixed.
2) Since the phi lattice in the B-spline filter is
often used as an output, I formalized this by setting
it as this->GetOutput( 1 ).

I also rewrote parts of N4 to try to flush out an issue
we're having on certain linux machines which helps with
readability.

Change-Id: Ic06e6e2227e1675d08e5fb13cbacbbc208fd3600
BUG: Uninitialized m_TransformDirection in ComplexToComplexFFTImageFilter.

Detected by valgrind.

Change-Id: I0506b17a392032fb80ca2e7d03f5eaa5c0a5ffac
Merge topic 'ComplexToComplexUninitialized'

5d6a1e04 BUG: Uninitialized m_TransformDirection in ComplexToComplexFFTImageFilter.
Merge topic 'MiscN4Fixes'

bd22bcf2 BUG:  Need to explicitly specify spline order.