handlePointerMove_ doesn't need to be called when dragging.
handleDragEvent_ takes care of the event in that case.
in handleDragEvent_, createOrUpdateVertexFeature_ doesn't need to be called for each dragged segment. it can be called only once with current vertex.
fixes made to pass the build
This commit fixes the bug that occurs when trying to modify
a closed LineString by clicking on the starting/ending node.
Such a closed line is added to the modify-test example.
Fix a bug in ol.interaction.Modify when trying to delete nodes
on a geometry that has duplicate nodes. A bug occurs when
clicking on the duplicate node.
