DarkThumbs: descargar versiones anteriores

- Fix typo preventing CB7 from working
- Add CB7 as a separate checkable option
- Add PHZ and GGB as supported extensions [tied to the ZIP archive option]
- NOTE: to enable PHZ/GGB, you must disable ZIP, click 'Apply', then enable ZIP
- Fix settings dialog box layout issues

Feature and bugfix release! Marked as "V2.0" because 7-zip is the new archive engine.
New file formats supported!
- 7z / cb7
- djvu
Issues addressed:
- #90 : zip files larger than 2G supported
- #33 : some zip files weren't working with Unzip
- #35 : "version is blocked" message when trying to install new version. Note: I still recommend the uninstall / install for preference, as a "replacement" install appears to require a Windows restart!
Known Limitation!
Currently requires being installed in "C:\Program Files\DarkThumbs" folder! If you want to install in a different location, you must copy 7z.dll from the install folder into "C:\Windows\System32".