Add AbstractCreateImg

AbstractCreateImg is an abstract class that creates an image from a type
and factory.  The logic to determine the size and values of the image is
implemented in the derived classes.  For example CreateImgDefault (which
has been modified to derive from AbstractCreateImg) creates an empty
image from given dimensions.
Add AbstractCreateKernel
Add CreateLogKernel

Added the CreateLogKernel class.  Creates a Laplacian of Gaussian kernel
that can be used for blob detection.  Ported from:

fiji.plugin.trackmate.detection.DetectionUtilities.

Permission granted by Jean-Yves Tinevez to change license from GPL.
Add CreateGaussianKernel

Creates a Gaussian Kernel.  Ported from:

org.knime.knip.core.algorithm.convolvers.filter.linear.Gaussian
DefaultCreateImg rename
Add SymmetricGaussianKernel
Add SymmetricLogKernel
Add KernelTest

KernelTest tests that the kernels run and asserts that the generated
kernel is the correct width.
Kernel ops shortcuts