Changes in Similarity/Equality-Filter: works now for images in the form of NDArray objects

Functions for similarity calculation: MSE, MAE, Chernoff for NDArray objects
Information about experiments: statistics can now be generated and saved as JSON file when LTM recording is used

ltm/detail/MemoryBase: added functions to write statistics about the filter used to a JSON file when recording of the LTM is disabled
ltm/processors/Processor: added SnapshotSimilarityFilter as case and function to put statistics about used filters into map that can be accessed by other classes
ltm/processors/filter/Filter: added struct for filter statistics
ltm/filter/equalityFilter/EqualityFilter: changed accept() function to work with new similarity functions, holds a queue of images now and uses similarity functions in aron/similarity, also added to the configure() method because there are new parameters

ltm/filter/frequencyFilter/FrequencyFilter: added functions to get basic information for statistics
plugins/Plugin: added call to getFilterStatistics() to allow for saving of statistics in JSON file when scenario is stopped
test/ForgettingExperiments: added function to print information about filter and usage of those into a JSON file

aron:

similarity/../NDArraySimilarity: similarity function for NDArray elements (images)
similarity/../chernoff: calculates chernoff measure of two NDArray elements
similarity/../mae: calculates mae
similarity/../mse: calculates mse

Signed-off-by: uhfpm_plewnia <uhfpm@student.kit.edu>