[571517] show top left on opening all graphical editors

With the new incremental growing canvas the default initial position of
the canvas my lead to strange results. For the FBNetwork editors we
already have the approach to show the top left corner with an offset.
This commit brings this code now to all graphical editors.

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=571517
Change-Id: I20b8fffc789f9f24c64277ede3b4e9cc3568629c
3 files changed