Add Python bindings

[arobsn]

Implement an API that is functionally equivalent to the Wasm bindings (ergo-lib-wasm). Essentially, this API should provide all the necessary functionality for dApps to build and sign transactions. Key features include:

• Transaction building
• Input selection
• Transaction signing
• Sigma Constants management and [de]serialization

[marctheshark3]

If I wanted to try this out, is it correct to fork the repo build this out, and then submit PR?

[sethdusek]

If I wanted to try this out, is it correct to fork the repo build this out, and then submit PR?

Yes, check out the bindings folder to see how other bindings are implemented, and the pyo3 crate if you're interested: https://docs.rs/crate/pyo3/latest

[0xf965]

Is this task already taken? @SethDusek are you currently working on it? If not, I can do it.

[sethdusek]

Is this task already taken? @SethDusek are you currently working on it? If not, I can do it.

Hi, I'll try to allocate more time to this issue soon. If I'm unable to I'll let you know. Thanks!

[sethdusek]

Implement an API that is functionally equivalent to the Wasm bindings (ergo-lib-wasm). Essentially, this API should provide all the necessary functionality for dApps to build and sign transactions. Key features include:

* Transaction building

* Input selection

* Transaction signing

* Sigma Constants management and [de]serialization

I've published documentation and an alpha version to pypi to try out (will be yanked before final release). I would appreciate any feedback on the interface https://ergo-lib-python.readthedocs.io