Add the possibility of setting the imagery offset numerically

[szali]

In some places (like Pápa, Hungary), the Bing satellite imagery may be off by as much as 36 meters. Correcting this requires a tremendous amount of arrow-clicking in iD.

This UI element needs a redesign. I would prefer a click-and drag approach like the one in JOSM (yes, here JOSM is more user-friendly), and that would be more accurate as well, since the arrows allow only a quantized setting.

But a textbox to set the exact offset is the most important thing! Think about returning users. They would be able to set the same imagery offset by simply copy-pasting a numeric value (like -36.78; 2.42). Now they have to click-click-click every time.

[bhousel]

Again, implementing #1124 would allow iD to correct the imagery offsets automatically, and I think would be the preferred solution for this.

[bhousel]

also this is a dup of #1340 anyway