More charts and improvements to existing charts

[lhelwerd]

Several ideas:

• Other chart types like lines or areas; statistics up to specific point in chart graphed across each position
• Comparisons/trends across multiple years (Chart analysis across multiple years #24, depends on JSON data from earlier years for full charts, stats charts and so on #11)
• Divide tracks per hour by 7, or other ways for histogram bin parameterization
• Sliders for histogram bin sizes to adjust them between acceptable ranges for that chart
• Other filters like subsets to select (Chart analysis filters #27)
• Relative weight for positions such that a drop from a high position is worse than one from a lower position, etc. Several analyses could be done with such a formula, such as biggest rises, drops and stable tracks, artists that have stable tracks
• Charts for one-day-flies and top contributors