This removes the isCore flag and allows us to dynamically calculate the
core flag for contributors.
For now this is just us (the first 6 contirbutors)
Also we do not need the default contributor anymore because the deploy
user has the role to manage contributors and can create the first real
contributors.
this mainly allows us to check if an account has a certain role and thus
if the account can call specific contract functions.
At some point we might want to extend that to support the check if an
account can call the function. For that we would need to have a mapping
between function names and roles, which we have not right now.
This allows use to call the methods with a string but still store the
name as bytes32.
I also had some issues when calling the methods from ethers.js and a
string parameter so this is easier and safer.
