Pass through PKCS11 config

[lnksz]

Don't try to be too clever or dictate strict ordering, etc. Just let the user pass in his PKCS11 URI.

Hint towards pin-source to avoid PKCS11 pins directly in the configs via pin-value

Close #12

[utkarshguptanxp]

@lnksz There are multiple reasons to have users follow a strict ordering, one of them being validation of the inputs. With this technique we are reducing the possibilities of errors by validating inputs and the URI thats acceptable to and been validated using CST. We will take inspiration from your contribution, especially related to other acceptable URI parameters, but we will not remove the URI preparation/validation logic.
@marioicastal FYI

[lnksz]

Of course go the direction you please.
Just something to think about:

• I also had to integrate in parallel with rauc for bundle signing. They leave PKCS11 setup to the user, (have great docs, though) and the integration was a breeze.
• This project is mainly a wrapper with config conversion and command execution. Just maybe, but something like Python or Go would appear to me as a more matching tool for the job.
• The URI builder is a school example function for unit testing, if you deem it worth the effort to continue the project in C, wouldn't be a bad idea to add tests.
• a gitignore to ignore build results would be nice

If you wish, I could send PRs for what you would like to change.