Electrumsv-sdk

- Fixed an issue to do with the python pip install process
which should allow for running the `electrumsv-sdk` command
as a global system utility (on system PATH).

- Basic functionality for automated installation and running of:
`node`, `electrumsv`, `electrumx` via the `electrumsv-sdk`
commandline script.
- Initial exploratory code for the `electrumsv-server` with faux API
intended to eventually cover all of the public API requirements of ElectrumSV.
The curio-based trinket framework was used for this initial implementation.