Add some more tooltips.
The 'delete output file' checkbox will now be enabled and disabled based on if the output FILE field contains an extension, rather than the output directory field.
Produce an error when there's an extension in the output directory field.
Not having an extension in the output file field but it not being empty will now also produce an error.
Get rid of some code that apparently made no difference (figured out after debugging).
The checkbox to determine whether or not there will be one output file for each found extension is now disabled once the output file field contains an extension.
The "The search directory field was left empty." error is now shown with an error rather than a warning icon.
Using the search button for the directory search field will now fill the proper field when selecting a folder.
We no longer force local boolean syncrhonizeDirFields to true after the user selected a file in the output file field, which would always synchronize the fields from that point on. It is now based on if the checkbox is checked again.