Set default axis limits in 2D-plots to the limits of the data

[TheExcalabur]

By default, pcolormesh and friends seem to not use tight boxes, leading to blank bars along the side or top of the figure depending on the range of values plotted. I see no positive results from this behaviour.

[shoyer]

This is also an issue for contour plots.

[Tillsten]

+1, always calling autoscale after contour & co should not be necessery.

[mdboom]

Related to #4891

[tacaswell]

This is going to cause interesting interactions with using margins by default.

[efiring]

It sounds like this is a proposal for the default to execute what would need to be a new "tight" mode in Axes.autoscale_view. Presently, None triggers tight scaling if the artists include images but do not include lines or patches. If I understand correctly, the suggested alternative mode would trigger tight scaling if the artists include or result from any image-like elements (e.g. collections such as quadmesh, or LineCollection or PolyCollection from contour or contourf). This seems reasonable. In its simplest form it would not be difficult to implement: the judgment would be based exclusively on the artists without regard for how they were generated. An alternative would be to add an attribute to artists that would specify whether they should be treated as image-like for autoscaling purposes.

[tacaswell]

This is handled in #5583