Multipage legends

By default a LegendsBlock must be contained in a single page. To allow it to span on several pages the overflow option can be used, setting it to true.

When this option is used you also need to define maxColumns, to fix the max number of columns on each page and maxHeight, to fix the maximum height of each column.

The LegendsBlock will be rendered on as many pages as needed to get all the items rendered with the given constraints.

Please note that if more than one page is needed, the second and following pages will only contain legend columns, without any of the other element of the page where the legends block is defined.