[gnome-builder] (9 commits) ...editor: implement session save/restore for editor

[Christian Hergert <chergert src gnome org>]

Summary of changes:

  e618d4b... session: synthesize success upon missing state file (*)
  09f6553... context: add workbench backpointer (*)
  2235038... context: whitespace (*)
  1a96883... context: set workbench after restoring (*)
  febd26c... context: keep unsaved file alive during function call (*)
  eeb4108... context: rely on session for buffer reloading (*)
  7aed518... workbench: delay addin cleanup until after saving session (*)
  a0fe992... layout: add helper to add view with a given stack position (*)
  59590cf... editor: implement session save/restore for editor (*)

(*) This commit already existed in another branch; no separate mail sent