So to make sx a single binary, I will make a new plugin architecture.

Each module will have its help text and own function.

We can then have a simple C API that uses strings and blocking function
calls. This will be a very simple way for people to create Bitcoin
applications too.

This is a wrapper around the libbitcoin libraries (another layer).

Reorganising all these projects will be a big task and needs some
pre-planning, so I'm going to wait until after my blockchain work to do
this.