Feature request: combine polygon tools into one (freehand and snapped)

[robinlovelace-ate]

It would be great if the these two UI elements could be combined into a single New Polygon tool:

In terms of UX user story:

• User wants to make a polygon
• Click on Polygon tool
• Woo it snaps!
• How do I put a freehand element where no roads?
• Aha tooltip or some other guidance that is visible but not intrusive tells me!
• Proceed to draw polygon, holding down Shift to draw points that are not on the network
• Job done 🎉

[dabreegster]

dabreegster/route_snapper#27 has implementation tasks

[dabreegster]

It took over a year, but done :) #549