bootstrap project

[zoedberg]

This PR is in draft because work is still WIP (not ready for a review). In detail I need to:

• complete README
• do a general code refactor/cleanup
• rework the transfers test
• wait for https://github.com/RGB-WG/rgb-std/issues/198 to be fixed and beta6 to be released (to avoid starting the project with submodules that point to PR branches)

I'm opening this to help debugging the issue reported in https://github.com/RGB-WG/rgb-std/pull/203

In the first commit of this PR all submodules point to the master branches, there you can see that all tests pass (except for 3 test cases that have been commented because they cannot work without a fix for https://github.com/RGB-WG/rgb-std/issues/198).

In the second commit rgb and rgb-std point to the invoice-pay2vout branches, there you can see that several test cases fail, with the error described in https://github.com/RGB-WG/rgb-std/pull/203#issuecomment-2137274571