API for pattern optimisations including pre-simulation should be streamlined. #493

It is good both to be explicit with optimisations and to provide a simple API to allow regular users to run a common routine.

For future consideration and discussion:

• Add transpile_swaps field to Circuit.transpile() to provide easy access to the transpile_swaps method
• Add optimize method to Pattern which runs a chosen regular sequence of commands (likely some combination of standardize and minimize_space)
• Add presimulate_paulis method to Pattern which runs the sequence of remove_input_nodes, infer_pauli_measurements and perform_pauli_measurements
• Add a method to Pattern which applies in-place the infer_pauli_measurements method (to avoid the requirement to write pattern = pattern.infer_pauli_measurements().