X axis label improvements

[aberridg]

Vertical/slanting x-axis labels, better calculation of how many labels/ticks to show. .gitignore

[arnaudspotfire]

Reviewed. Nice enhancement.

This request removes the ability to have horizontal x-axis labels.
This should still be possible and still be the default.

The x-axis lables do not align with the axis tick marks any.
If labels are short, there is too much space between the axis and the labels.
The height should adapt to the content.