Add Edit single feature ability

[savage13]

Add Edit one feature at a time

• Start Editing
  • Content Menu: "Toggle editing this marker or line"
• Stop Editing
  • Content Menu: "Toggle editing this marker or line"
  • Return KeyUp

This avoids the Leaflet.Draw editing all features using the toolbar. It becomes an issue when the number of features is large and/or the length of the lines becomes large.

This does not replace the Leaflet.Draw Edit ability.