BUG: Fix Coverity defects for LBFGS-B tests

This patch addresses the following coverity defects:
** CID 1186282
** CID 1186283

They are related on DeformableRegistration4&12 examples.
The cause of deffects was unchecked dynamic_cast.

Change-Id: Ifaa4211b1b2f07f6d8a30290428a31310d294791
Merge topic 'lbfgs-coverity'

d51263a3 BUG: Fix Coverity defects for LBFGS-B tests
STYLE: Remove deprecated python strel function

I removed the deprecated python strel function
The tests were updated to work directly with FlatStructuringElement
The 4 examples using strel were removed, the 2 binaryfilters were already moved to the ITK examples repo, I will move the 2 grayscalefilter examples soon.

Change-Id: I3fcec5168bcea5697945cc8402e75a1bfeefffea
Merge topic 'review-python-strel'

32ccbe4a STYLE: Remove deprecated python strel function