Fix 613 - Delete feature vertex on right click with menu

[adube]

Requires #4244 to be merged first.

This patch changes the way vertice can be removed from a feature.

Originally

The original behaviour was: on left click, delete the vertex immediately. This is the default behaviour in OpenLayers.

From now on

This behaviour has been changed to two ways:

1. on left click + ctrl (cmd on Mac), delete the vertex immediately.
2. on right click, show a menu with the Delete vertex item that, when clicked, deletes the vertex

Approval required The first behaviour was not originally specifically asked. It is a suggestion on my end for avanced users that are used to clicking on the vertice directly to remove them.

Affected tools

• GMF drawing tool (a.k.a. redlining)
• GMF editing tool

Technicallities

The way the detection of a vertex work is this: upon hitting a feature with the contextual menu event, we ask the ngeo featureHelper module to detect if the event occured on top of a vertex. The style of the vertex is used alongside the current resolution of the map view to return a buffered extent around each vertex of the feature.

If one of these extents contains the location where the event occured, that's a vertex hit. When that happens, we keep the indexes of the coordinate that hit to be able to delete it later.

The FeatureHelper has 2 new methods to help us in this way:

• getVertexInfoAtCoordinate
• removeVertex

[adube]

@fredj Fixes applied and rebased onto master.

[fredj]

Looks very good to me.
Let's merge with the ctrl click to delete. If needed, we can revisit this behavior later

[adube]

Excellent, thank you very much for the review.