Improve functionality of "Show in File Browser"

[telamonian]

Currently, right clicking on a dataset tab and selecting "Show in File Browser" will work correctly, but only if the dataset has a .data extension at the end of its name.

The likeliest cause is that at some point the related command for "Show in..." tries to find a file type to go along with the dataset, but only relies on the path to do so. Without the extension, no file type can be determined, so the command fails.

Fixing this will entail making changes (probably to core) such that the file type finding in this case is more robust.