ENH: Fixes for python 3 support

- The has_key method does no more exist for python3, it was just replaced by a normal "if 'WRAPITK_PYTHON_PATH' in" check.
- execfile() is deprecated in python 3, it was replaced by the newer exec() version (only for python 3)

Change-Id: I82773cf0ecd1ef68341f8c9c9460031bed372c6e
ENH: Updated Remote Module VariationalRegistration to new git tag

Change-Id: Ia39664b1dfdb6555373b7aaf3670bb9835a8d0df
DOC: Fixed HistogramThresholdImageFitler

Filter not Fitler.

Change-Id: I2178e4dcf0aba4bb012a67c15d182d4d1559ff4c
Merge topic 'FixFitlerTypoForRelease'

a2e95213 DOC: Fixed HistogramThresholdImageFitler
Merge branch 'MetaIO-update' into release

Change-Id: I39f84454acdfd00727581d02e0d74eb7ee82849d
Merge branch 'release'

Change-Id: I16aebdbf55794333e8c030067f29f932202816da
Merge topic 'Python3'

a5a09a9f ENH: Fixes for python 3 support
Merge topic 'variational_registration_update'

aeccb78e ENH: Updated Remote Module VariationalRegistration to new git tag