feat: Update to use latest c2pa-python SDK

[tmathern]

• Update to use latest c2pa-python SDK
• Update manifests used for signing (spec v2)
• Update signing code (use latest that c2pa SDK supports/has already tested in unit tests to make sure it works)

[crandmck]

I made some small copy edits to the README.

When I try to run the server with python app.py, I get an error.

    kms_key_id = app_config['KMS_KEY_ID']
                 ~~~~~~~~~~^^^^^^^^^^^^^^
KeyError: 'KMS_KEY_ID'

I guess I need to set up the env, but I'm going to approve because I don't want to block this PR and I don't have much time atm.

[tmathern]

I made some small copy edits to the README.

When I try to run the server with python app.py, I get an error.

    kms_key_id = app_config['KMS_KEY_ID']
                 ~~~~~~~~~~^^^^^^^^^^^^^^
KeyError: 'KMS_KEY_ID'

I guess I need to set up the env, but I'm going to approve because I don't want to block this PR and I don't have much time atm.

Yes, the (bare-metal/developer) environment setup is relatively involved. You need a bunch of environment variables set in the environment (there are some scripts that help set up the .env file that is read on startup). It is easier to use the Docker parts for a very quick start, as those have more defaults to run OOTB.

When I set it up, I nearly always follow the whole readme from top to bottom (and you know it is relatively long by now).

I realize you may also need some version updates, as I don't know which versions of what additional tools you currently have installed...