Convert transformations to position or displacement fields

[bogovicj]

Add methods to convert a general RealTransform to a RealRandomAccessible<RealComposite> (vf), interpreted as a PositionFieldTransform or a DeformationFieldTransform.

• The positions / displacements should be accessible so they can be saved as an array if needed.
• Use the updates to converters / RealComposite here (needs a new imglib2 release)
• Make new constructors for PositionField and DeformationField accepting a vf
  • reimplement using a vf
  • and RealRandomAccess<RealComposite>
  • remove existing constructors or convert to vf and call new constructor
  • convert with sequence of biconverters or a new type of view

[bogovicj]

In discussion with @axtimwalde and @cmhulbert today this will be a breaking change.

• The constructors will be:
  • (RealRandomAccess<Composite<T>>) and make copies of the acces
  • (RealRandomAccessible<Composite<T>>)
  • (RandomAccessibleInterval<T>) assuming vector dimension is first, and will boundary extend and linearly interpolate
• We considered a constructor that takes an OutOfBoundsFactory / InterpolationFactory, but decided against it (for now)

[bogovicj]

resolved by #42