Minor documentation changes
We will need a SortedSet rather than a HashSet : it will be easier to present the map to the user...
Remove setters in RecodedPenStroke. We know we won't have null values in
it, and we'll deal with RecodedLegend instances directly. Moreover,
setters offer the ability to change parts of the structure. That could
threaten its coherence. I think we don't need them : I remove them.
Adds a validation for RecodedDash, so that we won't put illegal values in our symobolizing tree