Update control code

It probably works...

All the Start/Stop/* functions for Actuator/Sensor have been removed and replaced with Sensor_SetMode/Actuator_SetMode. They shouldn't be called except from Control_SetMode, because Control_SetMode keeps track of the current state and prevents certain stupidities (like stopping an already stopped experiment).

Still to add:
* Dealing with emergency stop (set actuators to particular value (eg vent system)?)
* Experiment name sanitisation (User could specify "../folder_that_should_not_be_accessed_by_user/well_i_did_anyway" as an experiment name)
* Probably a good idea to stuff experiment data into separate folders based on experiment name? 

I've been staring at this code for too long =.=