Implementing the visitor pattern for categorized legends
Hiding/removing useless and unwanted constructors
Improves the typing of CategorizedLegend. This way, get, put and remove can be defined abstract in CategorizedLegend.
Adds getFromLower so that we can retrieve a coherent value for any input double
First steps towards a CategorizedLine implementation.
We currently mainly have a constructor and get. Good start.
Adds keySet in CategorizedLine
Checking that containsKey and containsValue work well
implementing put. putAll works as a result.
Improves the put method.
We want the merged map to behave coherently. To be sure we do that, we
perform an additional local push in the parameters.
Adds remove in CategorizedLine.

It seems to be complete already, thanks to the work made in
CategorizedLegend instances.