added 'keepShape' flag for connector, it disables connector recreate when it have 3 or less sections
added connector recreate when dragging section with shift pressed
Merge branch 'develop' of https://github.com/robertwaszkowski/gwt-connectors into develop

Conflicts:
	gwt-connectors/src/main/java/pl/tecna/gwt/connectors/client/drag/ShapePickupDragController.java