Implement a data centering option for time series bar charts

This adds an option to time series bar charts to set whether the value
being passed to the bar should be considered the middle, start, or end
of the bar. For instance, if passing values that are set to be end
values, the bar will be drawn so that the right side of the bar aligns
with the time point on the axis instead of the center.

Author: Dylan Nugent
Implement more useful value labeling.

Add independent value formatting for axis ticks and hover values on
charts that have axes displaying values. Ticks display unrounded but
SI-prefixed values, ensuring that two ticks showing the same value due
to rounding to a significant figure below the tick delta never happens.
Hover values show value to fixed precision of 2 numbers after decimal,
and formatting value for hover only can now be overridden with
"formatLabel" instead of "formatValue" variable to reflect that this no
longer updates the value formatting used on the axes.

Author: Dylan Nugent