Add ACL contract wrapper

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.

scripts/build-json.js

@@ -10,7 +10,8 @@ const files = [
   'Contribution',
   'Kernel',
   'Proposal',
-  'Token'
+  'Token',
+  'ACL'
 ];
 
 files.forEach((fileName) => {