Blacklist the libs section from package imports

Libraries never produce useful screenshots. Excluding by Debian
archive section instead of a lib* name pattern keeps applications
with lib-prefixed names (libreoffice, librecad, ...) importable.
With REMOVE_BLACKLISTED_PACKAGE set, the next import also removes
previously imported libs-section packages and their screenshots.

lib/tasks/import_debian.rake

@@ -29,6 +29,10 @@ BLACKLIST_SECTION_PATTERN = [
   %r{/?oldlibs$},
   %r{/?libdevel$},
   %r{/?cli-mono$},
+  # Libraries never make useful screenshots - and unlike a "lib*" name
+  # pattern this does not hit applications like libreoffice (editors)
+  # or librecad (graphics)
+  %r{/?libs$},
 ]
 
 # Whether to delete a blacklisted package from the database