Sync drafts between tabs

[josephmturner]

If two tabs are opened at the same time, it is possible to overwrite changes made to drafts in another tab.
Syncing drafts between tabs would be a nice solution. A simpler, less elegant solution would be to prevent the app from running in two tabs.

I removed syncWithLocalStorage logic in 18d4f9d because it would crash when a new reference point was created in different tab. The new reference point id would be added to the draftMessage, but the original point would not be retrieved from ushin-db.