Partially fix 1679452:

Partially fix 1679452:

  * drawing to or from a duck *within* a bline will adjust the offset of the newly created bline's layer to match the offset of the bline it's linked to

  * connecting two ducks, both within different blines will check whether the two blines have the same offset.  if so, the new bline will be created with the same offset.  if not, it will only be joined to the duck it started at

  * extending blines with non-zero offset still needs work

git-svn-id: http://svn.voria.com/code@307 1f10aa63-cdf2-0310-b900-c93c546f37ac