git repo/path for chain binary

[doggystylez]

currently the codebase object has keys for git_repo and recommended_version (referring to the binary version), however, the codebase is not always located in the root of the repo (./).

For example, agoric's repo is listed as https://github.com/Agoric/agoric-sdk/, and the source code for the (go) chain binary is located at ./golang/cosmos.

similarly, gravity bridge repo is https://github.com/Gravity-Bridge/Gravity-Bridge, while the code for the chain binary is located at ./module

I could see the path to the chain binary code defined as a separate optional field. Personally this would help a lot with automation