DOC: Edits for book 2 chapter 2.

DOC: Added SecondDerivativeRecursiveGaussianImageFilter example.

Change-Id: Ife86e17cd85ae5b8366d7ea71622d4fe5186674e
STYLE: Remove SORT macro in wrappings

The SORT option was added to cmake and we require a cmake
version which provides this native option out of the box.

Change-Id: I25612ce1be5beab1c806f9d609062b3cc4ba087d
Merge topic 'CleanupSort'

a7b6124c STYLE: Remove SORT macro in wrappings
Merge topic 'book-2-chapter-2-edits'

62ea1a48 DOC: Edits for book 2 chapter 2.