Extracts SIFT features from images using a FijiArchipelago Cluster
fileNames - a Collection of file names
This method makes no check of the validity of the filenames. For this
to work properly, they must exist within the Cluster file root, which
is indicated by FijiArchipelago.getFileRoot().
param - The SIFT parameters
An ArrayList of ArrayLists of Features, such that the ArrayList
corresponding to the ith file in fileNames is returned in the ith position here.