Taler HTTP API

We've implemented an HTTP API for our anonymous payment app Taler for
customers who wish to operate with Javascript disabled.  We thought this
might prove interesting to the WG.  

We're not actually trying to mirror the WG's Javascript API yet, due to
various things like the representation of amounts as strings being
unnecessarily dangerous. 

It's discussed a tiny bit in Sec. 3.2 starting p. 10 the paper at
https://gnunet.org/taler2016space which incidentally cites the WG a
bunch for background on other payments systems. 

See you next week in Lisbon,
Jeff