Source modules' code ports should be control parameters

[remram44]

Now that we have control parameters, it seems to me that some input ports should be changed. For instance, the code ports are urlencoded and meant to be edited from the configuration widget; showing them looks bad, editing them directly is useless, and getting/setting the parameter from code is awkward and already only works if it's a function and not a connection.

The main issue is that it completely hides where the data comes from, as there is no way to see control parameters in the UI (apart from the specific configuration widget).

[rexissimus]

I think this is a good idea. Control parameters are already visible in the diff. We could also show them in the "Module Info" tab like we do with annotations, but there is no room for it in the current layout...

[remram44]

Meeting discussion: let's do this, but should make sure that upgrade is super-safe.