The WebGL scatter plots should support multiline date axis tick labels

[monfera]

Dates in general need more space than numbers, and the truncation of dates is less clear-cut than that of numbers; also, breaking up numbers to multiple lines is very rarely desirable in practice.

SVG charts can already show dates in a multiline format, whereas the WebGL scatterplot cannot yet (see image below).

The original issue comment is associated with a PR (and a bunch of gl-vis PRs) that brought in the functionality of showing dates on WebGL scatterplots.

@etpinard conveyed the request that this issue be addressed.

Previous mentions:

• Code comment
• Related issue comment
• Overview of gl2d limitations, which this is an element of