BUG: Fixed a bug with zooming in charts

The zoom function was accounting for scaled data, but not shifted.
Introduced a new function to get a double precision transform for
things like zooming, and another to obtain a transform suitable for
single precision rendering.

Change-Id: I0d8a6bbd81db465cb89c1a8af9c8030c357aa05c
Merge topic 'fix-origin-shift-zooming' into master

74057f3d BUG: Fixed a bug with zooming in charts