[CoreWindow] add saveGraph action, add basic saveGraphToDB slot

DONE:
- rename saveGraph action to saveLayout
- add saveGraph action to file menu
- add saveGraphToDB slot for saveing only graph with original layout to DB
  and connect it with saveGraph action

TODO:
- saveGraph action was addet to separated loading graph from file from
  saveig graph to DB in future.
- 1. This will couse bugs, because user will
  have option save graph's layout without saveing graph before, that cause
  fail. There is no control if graph is in DB.
- 2. Repeatly saveing same graph cause adding original layout for graph in
  DB again. There is no control if graph is in DB before it's saveing.
- optimize DB setting on start and removing it form loading graph from
  file
[GraphManager] add test before saveing graph & layout

DONE:
- added test before saveing graph in method
  GraphManager.saveActiveGraphToDB to return if graph is allready saved
- added test before saveing layout in CoreWindow.saveLayoutToDB to return
  if active graph is not saved yet

TODO:
- separate saveLayout from CoreWindow to GraphManager
- in saveLayout when graph is not saved yet, add saveig it insted of
  canceling method
- optimize DB setting on start and removing it from loading graph from file