PyConf: Require options.simulation flag to be explicitly set by user to True or False

Currently the options.simulation flag defaults to True. If a users forgets to reset this to False when running over real data, the results can be rather insidious as the task will configure and quite probably run without any obvious errors. However, the task will not be picking up the correct conditions for the run in question which can lead to a number of difficulties which can be hard to spot and understand.

This MR thus makes the default None, and enforces the need for users to explicitly set this option.

• For tasks running over real data, users should already be setting simulation=False so any task exposed not doing this was anyway mis-configured.
• For tasks running over MC, this is where I expect to see the largest fallout from this as we will need to ensure simulation=True is set where-ever it is needed.