Reduce code duplication in Affine
Reduce code duplication in Affine

This patch decreases code duplication in the
parameter parsing of augmenters.geometric.Affine
by using the parameter handling functions in
parameters.py.

Additionally, most of the arguments of Affine
can now be list and will automatically be
transformed to Choice.

aleju/imgaug,aleju/ImageAugmenter,aleju/imgaug