[Taler] protocolv9 merged

[Christian Grothoff]

Dear all,

Just FYI: I just merged the 'protocolv9' branch into master. It is _not_
finished or stable, but stable enough for master ;-).

It completely breaks the protocol, with "small" changes like:
* support for extensions to contracts
* support for age restrictions (in principle)
* support for alternative blind signature schemes
  (cipher agility)
* various other minor fixes

Florian already updated wallet-core to match protocolv9.

I expect it'll take a few days for the dust to fully settle, so if
you're working on master, expect a few bumps (like the tests in
src/auditor/ are known to fail).

Happy hacking!

Christian