Add new index library

Merged Torsten Grote requested to merge grote/fdroidclient:index-library into master

This add a new F-Droid multi-platform index library that can parse V1 and V2 index, directly into memory or via a stream receiver.

Note that some features are only available for Android:

  • index signature verification (JarFile is JVM only)
  • index stream processing (InputStream is JVM only)
  • index V2 diffing (reflection is JVM only)
  • app device compatibility checking (requires Android)
  • app update checking (requires Android)

Other platforms besides Android have not been tested and might need additional work.

Edited by Torsten Grote