Move Toaster notification code out of onSaveToServer

[cpina]

The function onSaveToServer is currently saving the datapackage to the server and it's also showing the Toaster notification (where it informs the user that the datapackage has been saved correctly).

The functionality to show the Toaster notification should probably not be in the onSaveToServer but in higher, UI layer.

This might be handy to refactor if #3 is done: a function onSaveToServer without the notification might be needed in order to "Exit" datacreator-ui or to show the Toaster (depending if it was invoked via "Save to Server" button or "Exit package creator" and then "Save" if implemented in #3).