Implemented alignment by major unit in the time scale. This allows showing the first tick of a larger unit like days in a special way and is part of the basis of the time series scale.
* Make parseTime private
* start on fixing time scale
* Reimplement existing functionality
* Tidy tests
* Fix labels for non-linearly sized units
Months, quarters and years have non-constant numbers of seconds. A scale that's linear WRT milliseconds produces incorrect tick labels due to the label formatting losing precision (eg year labels lose month and day so a label of 2016-12-32 displays as 2016 instead of 2017).
* Re-implement tick generation
As in v2.5
