Enable quickly adding extra point on boundary while editing the boundary

[ekigamba]

Source https://github.com/onaio/kujaku/pull/349

• [ ] Enable faster adding a point between two points for more manipulation of the boundary eg. Adding a V between two circles/point requires adding an extra point between the two points and dragging the new point

Currently, adding a point between two points is possible but requires selecting the point next to the target location