18 rework metrics

[charliebtan]

Main changes:

• Remove the aggregate metrics
• Refactor CompletedJourneys (don't need to count per step any more)
• Fix WaitTime (had bug with off-screen waiting cars, also was dividing by wrong value for average wait time)
• Add a 'normalised' version of each metric (WaitTime is not truly normalised to [0, 1] but is divided by number of steps)
• Handles the two metric outputs in Simulator and Emulator

Minor changes:

• Move metrics.py to main dir - remove metrics dir
• Add an (i) to inferred params in dataframes (I think its good to be super clear about this - I had it set to infer and didn't know!)

One thing in the issue that I have not done is make the bayesopt loop explicit - I just made the extra outputs work with the built-in loop. Reasons for doing this:

• Changing to explicit loop changed the output (perhaps would still converge but wanted to avoid changing behaviour)
• I have seen the built-in loop has a few options which may be sufficient for what I need for report