Closes #13 - added bar chart and chart picker dropdown based on data types plotted
Closes #5 - added support for grouped bar charts on identical x label
Fixes #7 and fixes #8 - defaults to origin on bar charts; both origin/log buttons work per usual
Correctly matching keys on bar chart ordinal scale - fixes #5
Closes #6 by removing Y2 from GUI; also adjusted Origin and Log Scale button group titles to be titles, not buttons
Almost finished issue #10. Need to do some quick further testing.
Fixes #13, closes #10, resolves #9 by allowing all chart types when x-axis is quantitative and fixing series logic for 3+ variables
Merge pull request #15 from jaericson/wip-barchart

Bar chart and several improvements to ChartView