Added code to deal with rendering double precision data

This uses an approach where the axes retain double precision data, and
coordinate with the vtkChartXY and vtkPlotPoints classes to scale the
data appropriately. This required some refactoring of the code dealing
with calculating the bounds and arranging the data ready for being
rendered. Functions that modify the plot transforms required some
enhancement to use the scaling factors when necessary.

Change-Id: Ic084d9dab7f02ded82187bd6207a3f837fef03ec
Added a test exercising the rendering of tiny numbers

Change-Id: I34ebfd9381302754da3ef808748b34dbdcabf8cc
Merge topic 'charts-double-precision' into master

082acecc Added a test exercising the rendering of tiny numbers
01a26ade Added code to deal with rendering double precision data