Add to the GUI the option to process several files at once

[phydev]

• Rename the "Open" button to "Open file" and create "Open directory" button
• Add an argument to action "get_file" that distinguishes if we are opening file or directory
• Add partial(self.get_file, file_or_dir) to find_bt and to the new button find_dir_bt
• Write a function to process the csv files in the directory path.

[phydev]

• Processed data should be stored in a single csv file.

[phydev]

Done in commit #0604164