Rename events to be consistent

- Make State.save() always throttle calls -- since that's the common
case.

- Immediate saves are now the exception, with State.saveImmediate().

- The function is called State.save(), so the dispatch event should be
'stateSave'.

src/main/index.js

@@ -102,8 +102,8 @@ function init () {
 
     app.isQuitting = true
     e.preventDefault()
-    windows.main.dispatch('saveState') // try to save state on exit
-    ipcMain.once('savedState', () => app.quit())
+    windows.main.dispatch('stateSaveImmediate') // try to save state on exit
+    ipcMain.once('stateSaved', () => app.quit())
     setTimeout(() => {
       console.error('Saving state took too long. Quitting.')
       app.quit()