Custom goals support

Currently a world author is constrained to only use the pre-defined goals. This makes world authoring more rigid than it should be, as it’s not easy to add new goals, or alter the existing ones. A world author needs to have access to the server in order for her to do this. In order to encourage faster development of goals we should add the ability for a world author to define complete Python goals per NPCs. The server should then evaluate the code sent.
This feature should be possible to disable. It should probably not be turned on by default even. We also need to make sure that the Python sandbox is safe enough so that no malicious code can be run.
Note also that this feature would in some way go against the “natural language” aspect of cyphesis design, since it won’t be easy to transfer these kind of goals through natural spoken words. However, this is a sacrifice we’re willing to make in order to make the development of the world move faster. The idea is that this feature is mainly meant to be used for prototyping and testing out ideas. Once a goal seems solid it should be moved into proper Python files on the server.