Merge branch 'support-all-signing-key-types' into 'master'

support all APK signing key types: DSA, EC, RSA

The lovely python getsig replacement was only looking for .RSA files, but the signing key is defined as: "A signature block file with a .DSA, .RSA, or .EC extension"
https://docs.oracle.com/javase/7/docs/technotes/tools/windows/jarsigner.html

For more info:
https://f-droid.org/forums/topic/binary-repo-whatsapp-error

See merge request !51

diff --cc fdroidserver/update.py
Simple merge