- taler-offline-tool now handles extensions
- command "extensions" added with subcommands "show" and "sign"
- parses extensions from taler config
- shows and signs of extensions and their configurations
- creates signed set of configurations for upload
- added test for retrieval of extension config
- simplified signature verification for extensions
- remove per-extension signatures, also from DB schema
- adjust prepared statements accordingly
- adjust DB event handler for extensions
- allow NULL for config for extension in DB schema
- handler for /management/extensions adjusted to new datastructures
- changed test for TALER_denom_blind/TALER_denom_sign_blinded with and
without TALER_AgeHash
- minor updates and various fixes
