Implement a progress bar and a checkbox to enable/disable the progress bar (default checked)
Re-enable the search button when there were no files found
Show a different error if no files were found when certain criteria's were given but not met
The extension field is now always lowercase even if the file has an uppercase extension (example_file.TXT -> extension will be shown as '.txt' instead of '.TXT' in ListView)
Double-clicking on an item in the results now prompts you with a yes-no whether or not you want to open the file and if you press yes, it opens the file.