This makes sure there is a GPG signature on any file that is included in
the repo, including APKs, OBB, source tarballs, media files, OTA update
ZIPs, etc. Having a GPG signature is more important on non-APK files since
they mostly do not have any signature mechanism of their own.
This also adds basic tests of adding non-APK/OBB files to a repo with
`fdroid update`.
closes#232
`fdroid update` should be able to handle any valid filename (hopefully
aapt doesn't barf on them). To handle that, the environment where the
shell commands are run in needs to have a UTF-8 locale set. If LANG is
not set, things default to ASCII and UTF-8 filenames fail.
This also renames test APK with lots of Unicode chars as a test case.
closes#167
