use CanvasAxisTickRenderer for burndown x-axis to fix label rotation

fixes #810

Not sure the reason why this got commented out at 56789e70018f4ab474f03ca6c0f0814e1ab13409
show as much as possible for sprints in sidebar
remove labels from sidebar burndown
catch some weird jquery unrecognized expression error.
Merge branch 'patrick/ui/chart-labels'