Runtime System Modifications

[milanofthe]

PathSim already supports adding and activating/deactivating blocks and connections at simulation runtime. For example through events. Whats missing is the capability to cleanly replace and remove blocks in a similar fashion.

What this will enable:
Imagine you are running a big system simulation with many (maybe hundreds) of blocks that might be small or large individual models themself. Some of these blocks might be surrogate models, i.e. trained neural odes. The described functionality would enable seamless hot-swapping of models mid simulation. For example a nn that has been trained on some real world data and update the surrogate model every couple of minutes with the newly trained nn.

[milanofthe]

Implemented: add/remove blocks & connections at runtime, activate/deactivate via on()/off(), parameter mutation via @mutable, lazy graph rebuild. All covered by tests.