Automatic Visualization Selection

[alexsb]

We should consider switching all visualizations to “auto” and pick the best one based on some heuristics about the data.
We could also automatically determine whether the label should be on/off.

Generally, this should be fairly easy, mostly just fall back on defaults.

Two rules that I'd suggest:

• distinguish between large C categorical (Default Vis for categorical column with large N: Text #490) and small C categorical; (New Default Small-C Categorical View #488)
• Show labels for categorical data if C > 5
• Use group size as default for label groups, but if there are re-occuring labels, use the example/count by default (Group Visualization for Labels #497)