Add ability to attach notes by important changes on the Dashboard#48

This is similar to how it works in Google Analytics. If you made some changes that can impact on your traffic or Google Core Update happened, you can add a note, so then you can understand why traffic, positions increase or deacrease.

It is a good feature as for Dashboard, such for Rank Tracker

It’s already added to Rank Tracker.

The feature is added in Dashboard 2.0 and is available for usage. Soon Dashboard 2.0 became the default dashboard and the old one will be deleted.