fix#2232
A classified layer needs to have compiled the data to known its
classes/categories.
This commit review the way we build the legend: instead of creating
with the whole caption panel, we just set a container and we populate
it later. This opens the door for live changing the legend when
editing the layer.
But we have to clarify that "reactive" pattern at some point, as we
have some concurrent pattern laying around: the `render()`, which
coupled with the schema and this is nice, but for now it's a bit rough
(changing the whole UI each time); the `propagate` way, which is
more specific, but not coupled to the schema; the `dataChanged`; and
the `onDataLoaded` now, which is a bit different, as it's about the
data being loaded, not changed/modified, but for the DOM it may at
the end be the same. Well, food for thoughts…
cf https://forum.openstreetmap.fr/t/umap-2-3-changement-de-gestion-des-pop-up/23680/3
Trying to make this panel expanded/condenses thing simpler and more intuitive.
It's mode can be set:
- by explicitely setting defaultPanelMode = xxx
- or, if defaultPanelMode is undefined, with sensible default when there is
an onLoadPanel defined, and to respect previous uMap behaviour
- or, if defaultPanelMode is unset, and some feature opens in the panel, it
will be set to expanded (here again to respect previous behaviour
- then, when user change it manually (by clicking on the toggle button), then
we should never change it automatically, and respect the previous mode when
reopening the panel
(We are only talking about the left panel, here.)
