PERF: Refactor some deletion code

These changes should be functionally equivalent, but are non-trivial and
should be tested.

Part of issue: https://issues.itk.org/jira/browse/ITK-3182

Change-Id: I534201282cba84cd93dfbc2bdd581127c03e635d
BUG: GDCMImageIO ignore image orienations from MetaDataDictionary

GCMImageIO can transfer DICOM tags from the MetaDataDictionary
to the DICOM files. However, itkImage attributes of Origin, Spacing,
and Directions are handled specially. Unfortunately, they are also handled
inconsistently.

For Origin, preference is given to DICOM tags in the MetaDataDictionary
over the ITK_Origin entry in the MetaDataDictionary.

For Directions, preference was given to the ITK_ZDirection entry in
the MetaDataDictionary over the DICOM tags in the MetaDataDictionary.

This patch unifies the behavior so the DICOM tags in the MetaDataDictionary
take precedence over ITK_Origin and ITK_ZDirection.

(Note that for Spacing, preference is still given to ITK_Spacing.)

This patch addresses the bug in the 3D Slicer #3254. See
http://na-mic.org/Mantis/view.php?id=3254

This patch set includes a test.

Change-Id: Ibe8cb7dcd7387ba696ba509bd328bca2d77d1831
BUG: Enable slice-by-slice streaming for ShrinkImageFilter

The ShrinkImageFilter was requesting a larger region then required for
it's inputs. One use of the ShrinkImageFilter it to connect it's input
to a SeriesImageReader, by streaming slice by slice files can be
skipped. This patch fixes this usage so that only the information used
is requested and loaded.
DOC: Migration guide is updated for multi precision of ITK

New changes breaks the old transformFileWriter/Reader APIs when they are
used to read/write a float type transform.
Previous APIs still work for reading/writing a double precision transform.
These new changes are reflected in migration guide.

Change-Id: I60afcdd40c258d7f31a42cff8e129ee84d511183
Merge topic 'FixShrinkImageFilterSliceStreaming'

61fec8c BUG: Enable slice-by-slice streaming for ShrinkImageFilter
Merge topic 'UpdateMigrationFileForMultiPrecisionVersionOfITK'

5ab4c36 DOC: Migration guide is updated for multi precision of ITK
Merge topic 'Delete-Refactor'

07747a0 PERF: Refactor some deletion code
Merge topic 'GDCMImageIOOrientationsFromMetaDataDictionary'

2c76100 BUG: GDCMImageIO ignore image orienations from MetaDataDictionary