COMP: Fix all valid cppcheck warnings in "Module/Filtering" directory

cppcheck is run inside the ITK/Module/Filtering directory and all the
valid cppcheck issues are fixed.

Some of the cppcheck warnings are related to the functions that are not
used, but they may be used later by users. Such a warning is an example
of an invalid warning.

Some warnings are related to the intentionally created issues that are
provided in the test files. Such warnings are another example of what I call
invalid warnings.

The titles of major fixed issues are listed below:

- if possible, variables are passed by reference.
- prefix ++/-- operators are preferred for non-primitive types.
- initialization to assignment is preferred.
- if possible, the scope of variables are reduced.

All the ITK tests are passed after the above changes.

Change-Id: I2ccc197141fdaa1cc4b70bfab20d5c87a5cf72ca
ENH: use find_package(DCMTK NO_MODULE)

I have a patch submitted to the DCMTK people that generates a proper
DCMTConfig.cmake such that find_package(DCMTK NO_MODULE).  Starting
from that, I've verified that ITK can build itself using NO_MODULE and
that furthermore, all DCMTK libraries and DCMTK library dependencies
are pulled through properly and exported when ITK is installed.

The NO_MODULE changes are actually incorporated into
Modules/ThirdParty/DCMTK/CMake/FindDCMTK.cmake which will try
NO_MODULE and fall back to the old method to find libraries and
include directories.

Change-Id: I740268a9116cc6e4152c38cfc3d6d5252abc512e
COMP: Fix all valid cppcheck warnings in "Module/Segmentation" directory

cppcheck is run inside the ITK/Module/Segmentation directory and all the
valid cppcheck issues are fixed.

Some of the cppcheck warnings are related to the functions that are not
used, but they may be used later by users. Such a warning is an example
of invalid warnings.

The titles of major fixed issues are listed below:

- C-style pointer casting are converted.
- initialization to assignment is preferred.
- a default constructor is added to classes that did not have any
constructor.
- unused variables are removed.

Change-Id: I7222f7d8539a840533a69bba4507854d57f9104b
Merge topic 'DCMTK_NO_MODULE'

57a4489 ENH: use find_package(DCMTK NO_MODULE)
Merge topic 'cppcheck_filtering'

675912d COMP: Fix all valid cppcheck warnings in "Module/Filtering" directory
Merge topic 'segmentation_cppcheck'

227e6be COMP: Fix all valid cppcheck warnings in "Module/Segmentation" directory