Allow agents to manipulate themselves

[TimKam]

In the current JS-son version, all updates to an agent's beliefs are processed by the environment first, i.e. an agent can only update its own beliefs by requesting the update through the environment. Updates of plans, desires and preference functions (the preference function generates the agent's intentions based on its desires or beliefs) are not possible.
A new feature is planned to be implemented to change this. Agents should be able to manipulate themselves with no restrictions, directly via their plans. Because this feature enables an extreme degree of dynamic evolution, agents should be configurable to not support this feature.