Adjust campaign mode start difficulty

[s-c-orr]

The first bot pitchers that new players face in the campaign are too difficult. To adjust:

• Move the coach bots from the practice tab to the campaign tab.
• Get rid of the practice tab and the 'practice' option on the launch screen.
• Should we mark the coach bots as being separate from the campaign, but a recommended starting point? Or should we add them to the campaign (set win conditions; adjust the progress bars)?
• Add information to the UI so that players understand that bots pitch in a repeating cycle that they can solve.