Image preprocessing for VGG

Image preprocessing for VGG neural network.

The node expects a flow variable "currentColumnName" to define the column, which has to be preprocessed.

Mimic "preprocess_input" from
https://github.com/keras-team/keras-applications/blob/master/keras_applications/imagenet_utils.py

Input ports

1. Type: Table
   Input data table
   Input data table

Output ports

1. Type: Table
   Output data table
   Output table with one column of images preprocessed according to VGG requirements