Returns a geometry that is formed by moving a vertex on a simple line geometry.
The vertex to be moved will be the one closest to the point specified by the second parameter. The third parameter specifies the point to which the vertex will be moved.
This function will only move one vertex on the geometry and so may leave a spike. For smoother results, consider the drag_vertex function.
Parameter 1 - a simple line geometry.
Parameter 2 - a simple point geometry identifying the vertex on the line to be moved.
Parameter 3 - a simple point geometry identifying the new location for the vertex.
Returns: the resulting simple line geometry after the vertex has been moved to the specified location.
Note: This function does not fully support 3D geometries. Any 3D geometries will be projected down to 2 dimensions.