leaflet-styleeditor div not child of leaflet-control-container div

the `leaflet-styleeditor` div is not a child of the `leaflet-control-container` div like other control. (see for example the zoom control).
It also needs the class `leaflet-control`

this causes the styleeditor to gain attributes of the standard `leaflet-container`

I added the option `editorPosition` which controls where the editor div will be placed. For now only `topright` is feasible, as the other positions would need some changes to the css.