Insight Toolkit : Changed version to 4.4.2 and added python wrapping

Here is a new version of the formula which enables python Wrapping.

In my last try (https://github.com/Homebrew/homebrew-science/pull/186), the problem was that the formula depended on a head-only gccxml. Since ITK 4.4.2 this was fixed, a working version of gccxml is installed when ITK_USE_SYSTEM_GCCXML is set to OFF.

The changes done in this PR are the following :

* Changed the version to 4.4.2
* Added python support with the new python syntax
* Solved the ITKVtkGlue problem with a patch (can be removed when ITK 4.4.3 is out)
* Added itkv3 compatibilty option
* Added vtk dependency

Note : the only error I get from brew audit is :
> Use "#{ENV.cxx}" instead of hard-coding "llvm-gcc"

Without setting llvm-gcc the build will fail.

Ping @scicalculator, @samueljohn and @brotoes