Split the python wrappers into separate modules

We don't want anything which does dynamic memory allocation in the library.

* We only use 8-byte MACs
* The version byte is \x03, not \x01

Remove the (now non-functional) declarations of olm_set_log_level in the C and
js wrappers.

Concerns have been raised that including logging functionality makes it harder
to audit the implementation to ensure that no secret information is leaked. We
are therefore removing it from the master branch.

Make a few bits of the Olm spec a bit clearer

It would be nice if the tests tested what we'd built, not something different.

This fixes an incorrect re-declaration of ed25519_sign.

Implement header files for some of the other library bits so that we don't need
to declare functions in crypto.cpp.

something about 'global' not defined

Build into 'javascript' dir and tell package.json exactly which files we care
about.

switch from /usr/bin/python to /usr/bin/env python. this doesn't help folks whose python path points at python3 (e.g. Arch linux) though, but I see no choice than they have to change the shebangs, as we do on Synapse.  For instance, OSX doesn't have a python2 symlink, otherwise we'd use /usr/bin/env python2 shebang.

Add a basic specification for the olm protocol and format.

Replace hard coded references to the 32-byte key length with a constant, add utilities for copying data to and from fixed sized arrays