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.