Improve TopologicalStyleProvider

[flo-dup]

Do you want to request a feature or report a bug?
Feature / bug

What is the current behavior?
TopologicalStyleProvider shows the connected components of the power grid, by using different colours for busNodes only if they are not connected through lines, which is not that interesting for the user (except voltage levels far away one from the other, each voltage level is more or less connected through lines to the other neighbouring voltage levels of same nominal voltage)

What is the expected behavior?
TopologicalStyleProvider should give different colour styles for each bus node of a voltage level node, and no propagation of the colours should be made. Hence, parameters styleMap and baseVoltagesCounter can be removed, and each method using those too.
The styles for bus nodes should start from 1 (.nad-vl50to70-1 for instance), busNode.getIndex() + 1 can be used for it. Keep 0 for the edges (.nad-vl50to70-0 for instance).
This is not that topological anymore, so this should be probably renamed. Maybe VoltageStyleProvider? as each busNode of a voltage level has the same nominal voltage but a different voltage / angle.

What is the motivation / use case for changing the behavior?
Better seeing the bus nodes.

To go further this would be even better if the start of the edge had the same colour as the corresponding busNode, but that's another topic.