#117 Taylor diagram

[Jean-Marie Epitalon]

Hello,

- there is no way to check if a taylordiagram method
already exists with a given name
no function call like: canvas.listelements
("taylordiagram")

- size of markers identifiers, set with
"td.Marker.id_size", is not definitely defined by this
attribute value: it seems to change with the scale
along "Standard deviation" axis.
It is not what we want since the total size of the axis
on the page does not change with the scale: only the
tickmarks and their label vary with the scale.
The symbol size should not vary.

Regards,
Jean-Marie