Archiver plugin update and review:
- updated to support some of the compression formats up to libarchive 3.2.2,
- detect libarchive 2.8+ using pkgconfig,
- use alertpanel API instead of creating gtk dialogs from scratch (with missing
- dialog title, and no clue about what is displayed),
- configure script now makes use of libarchive pkgconfig,
- fixed wrong use of cached page struct info, we do now rely on data set in widgets
to get source folder and target archive filename and sync the page struct info w/ it
when needed,
- renamed gzip/zip to gzip,
- reworked the way archive formats and compression formats lists are displayed (not translatable anymore).
- reformat code a bit.