Update gitty restriction rules

After implementation of the restrictions, we had more discussion on the topic, and concluded that there were some improvements that should be done for the git restrictions.

We now want that:

• WIP branches stay an implementation detail, and should not be pulled by users
• No force push is allowed
• New branches can be created, provided they follow the feature/[anything] naming
• Master can be pushed to, it'll be protected in the future.