RFE: Export filtered segments

[ugcheleuce]

At the moment, when a Navigation mode is selected (e.g. Search or Quality Checks), the Enter key jumps to the next matching segment, but Virtaal still shows all segments. If there are many segments that match the filter, the user has no alternative but to juse Enter multiple times to jump to the each next matching segment.

Often, when simply checking things, it would be easier to be able to just see all matching segments in a single list, without the other segments.

To accomplish this, I suggest that a feature is added to Virtaal that exports the currently filtered segments to an outside file. This export file is only for reference -- my suggestion is not to make it possible to merge the exported file again (as one would be able to do with the Translate Toolkit tools).

The most user-friendly export format would be an HTML table, but if that is not possible/too difficult to code, then a PO file or a file in the currently opened file's own format would be okay as well. The advantage of an HTML file or a plain text file is that users won't be confused by the fact that they can open the export file in Virtaal as if the file is something that should be edited.

The export should be available for the currently selected filters. For example, if three quality checks are selected, then the export file should contain only the segments that match those three checks. Or for example, if a search is currently active for the word "load", then the export file would contain only the segments that contain the word "load".

As an added bonus, Virtaal could automatically open this file in the user's default browser, but that is not essential.