Added component directory and subjectHeader

- created directory structure for components
- added a subjectHeader component
replaced header in start page with subjectHeader
replaced header in continuousMarket with subjectHeader
Added revealedPreferences configuration
slight modification to Finish page

changed the selected payoff table cell to show points / 3.
Added more offer acceptance validation

Added checks to make sure that subjects can't buy more than they can afford, or sell
more than they have.
Merge branch 'components' into aws
Merge branch 'continuousMarket' into aws