handwriterRF (development version)

Major changes

Created compare_documents() to compare two handwritten documents using either a similarity score or a score-based likelihood ratio as a comparison method.
Created function compare_writer_profiles() to make experiments faster on large numbers of documents compared to compare_documents(). compare_writer_profiles() calculates either a similarity score or score-based likelihood ratio for every pair of documents.
Created new data frames of writer profiles train, validation, and test. Created a new random_forest from train. Created ref_scores, a list of same writer and different writer similarity scores, from validation.

calculate_slr() has been superseded in favor of compare_documents(), which includes the functionality of caclulate_slr() and offers additional functionality.
Created plot_scores() to plot histograms of the reference same writer and different writer similarity scores in random_forest$scores.
Deprecated get_cluster_fill_rates() in favor of handwriter::get_cluster_fill_rates().

Removed quotes around "same writer" and "different writer" in documentation.
Removed dontrun{} from the examples for random_forest. Changed example for get_distances() to something that runs in less than 5 seconds and removed dontrun{} from this example. The examples for calculate_slr() take longer than 5 seconds to run so dontrun{} was changed to donttest{} for these examples.