also covered by test

Added more detailed contracts to better understand Coconut's zk-SNARKS flow.

still problems with windows executable

also added more tests for zencode_data, normalised the syntax of ECDH
and ECDSA and completed the documentation

return 0 on success, 1 if error (as shell script default)
also removed old dockerfile

🐹 Golang bindings

🔨 Adding check-py target, for python test

added study on random quality and way to quickly benchmark

much cleaner zencode realigned to documentation, dropped esh for
templating docs directly in mkdocs, updated all tests and examples,
new shell script example page, reorganisation of zencode docs

python2 is out on OSX