see #10205: Strange align nodes in circle behavior
allow to define center node also when a single unclosed way is selected
add robustness and more unit tests for evaluation of valid selections
if only nodes and no way are selected, order the nodes using the angle to the agv. east-north position. This should produce a predictable result
if way(s) are selected the order the nodes is determined by the occurence in the way(s). Self-Intersecting polygons are rejected if no center node is given
don't throw InvalidSelection when selection is valid but no point was moved, let buildCommand() return null instead
With a selection that gives a center point and way(s) which are not even close to a circular shape the result might still be surprising. Sometimes the way nodes are arranged around the center node, sometimes they are moved so that a circle arc with nearly the same length is produced. The result changes significantly when the way nodes are also selected. Subject to further improvements.