Add a "Save Layout" button on the Layouts pane

[annaritz]

Currently, the only way to save a layout is to enter the Layout Editor from the Layouts pane.

However, I often want to save the layout that I just generated (either manually or through the automatic layouts). To do this I need to enter the Layout Editor and immediately exit the Layout Editor (the dialogue box asking to save the layout pops up then).

In fact, it would be nice to save a layout at any time.

[lohani2280]

@annaritz @adbharadwaj I would like to work on this issue.

[jlaw9]

@lohani2280 you may be able to use code from #271 as it adds a save button to the layout editor mode