BUG: Expose BSplineInterpolateImageFunction test

The BSplineInterpolateImageFunction function does not alway produce
the correct answer when the image direction cosines are not
the trivial identity matrix.  This is described in jira issue
https://issues.itk.org/jira/browse/ITK-2889 reported by
Marius Staring.

In addition, some common code was extracted to the makeRandomImageBsplineInterpolator.h
and non-trival direciton cosines are being used for the itkRandomSource
image to improve the amount of stress test provides.

Change-Id: I05417dbe7c87e9577954679c481ff3c29a9cc291
BUG: B-spline interpolator should use direction

The BSplineInterpolateImageFunction class has two functions to compute
the derivative:
- EvaluateDerivativeAtContinuousIndex
- EvaluateValueAndDerivativeAtContinuousIndex

The first one does take direction cosines into account, the other does
not. When called while using an image with a non-trivial direction
cosines, the two derivatives are not equal.

I believe this bug was introduced a long time ago by commit 6abbc7969a90786c4c73f5d191f634db536c2d1d

Change-Id: I9300e7fe75b22c8d44b87cdb0189f7ae47fd59fb
Merge topic 'ExposeBugWithTest'

4c520ca BUG: B-spline interpolator should use direction
ded8beb BUG: Expose BSplineInterpolateImageFunction test
PERF: avoid doing GetPoint and SetPoint for the same point

Store the points container into a temporary object, then get a reference on the
point and do whatever.

Change-Id: I8293f956da97ae7bd015861f512ba3d069e1219a
Merge topic 'ExposeBugWithTest'

5aeb6bd PERF: avoid doing GetPoint and SetPoint for the same point