added functions for counting letters
added exception handling for file opening; in count_* functions added parameter for possibilty to count many files in one dictionary; added two functions for searching all given directive
added function for printing all results to file
Added function main, where is processed input parameter; fixed bug in print_to_file function (variable dictionary  needs to be set to empty) and added parameter for passing directory
deleted uselees line wchich was erasing data from overal statistic