Highlight GeoPoints at dragging (e.g. for lines)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34964 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #3874: at least the code should work for GgbScript; JsScript is harder and may be prohibited to use with Insert file, if we have little time

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34965 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #3874: error in my previous commit in this ticket

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@34966 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e