Creating an horizontal layout for legends

Using some config.yaml configuration options in an unusual way it is possible to have a layout for legends that is horizontal, instead of vertical.

To get this behaviour is necessary to:

• use the legend block maxHeight property with a very low value (e.g. 1) to force a new column for each legend item
• use the legend block maxColumns value to choose the number of columns for the legend (a new row will be forced after maxColumns is reached)