BUG: Address Coverity warning about null pointer dereferences

The patch addressed the following Coverity warnings:

** CID 1243373:  Explicit null dereferenced  (FORWARD_NULL)
itkTIFFImageIO.cxx:
1192 in itk::TIFFImageIO::ReadTIFFTags()()

** CID 1243372:  Dereference null return value  (NULL_RETURNS)
itkTIFFImageIO.cxx:
1096 in itk::TIFFImageIO::ReadTIFFTags()()

** CID 1243371:  Dereference before null check  (REVERSE_INULL)
itkTIFFImageIO.cxx:
1100 in itk::TIFFImageIO::ReadTIFFTags()()
Last login: Fri Oct  3 19:47:29 on ttys004

Change-Id: I02c8435628c860ff03889b9b57e9dd1543bf82da
ENH: Remove support for TIFF tile as 3D and dead code

This TIFF file format is a file which contains a list of directories,
if there are no directories in the file it's not a valid tiff. Code
which supported 3D tiles was conditioned on a file with no directories
and no data. Additional code was removed related to a private SGI tag
TIFFTAG_TILEDEPTH, ImageJ specific tag also pre-conditioned on this
invalid case.

Change-Id: Id4ef171c5dbe0c797be206e0059c7488719ef6e6
ENH: RGBA read images should stay unchanged.

The image that are read with the TIFFReadRGBAImage should not have
their pixel types converted. This libtiff method always read images
into an ABGR uint8 format. When the tiff file is read by this method
it should report that uint8 and RGBA is the component an pixel type
for the image. This allows the standard ITK buffer conversion to be
performed.

This change remove extra cases and template instantiations.

Additionally the RGBAImageToBuffer method was flipping the image along
the y-axis, this has been more explicitly done with the call to
TIFFReadRGBAImageOriented.

Change-Id: I022b12921d406edb09730f905213b0db811f1bd4
BUG: Extent a test to reflect multi-metric registration bug

In this patch the "itkSimpleImageRegistrationTest2" is extented to use
an additional rigid registration stage with a multi-metric that contains
only "one" metric component.
This test is supposed to show a bug in ITKv4 registration framework when
it is used with multi metrics.
This test will be failed by returning an exception because current
ImageRegistrationMethodv4 always assumes that multi metrics have more
than one component when it tries to set the metric sample points.
Also, in the extented test, the multi-stage registration is implemented
in a cascaded way that is different than the methods used in other
existent tests, and it can be a bonus itself.

Change-Id: Ibfa9b5c65794ec5cf369c9aef84bb822eca799f0