Make iD default (clean PR)

Let's make iD default. If a user misses the drop down, and just clicks on "Edit" they should go to iD, not Potlatch 2.

- We had a great testing period
- iD's doing much more to onboard new users and we want to particularly reach new users who might miss that there's a drop down.
- iD is the first one in drop down list but isn't default.

This PR just modifies the example config.

![](http://cl.ly/image/2w3m0U1E1Q03/Screen%20Shot%202013-05-07%20at%2010.29.22%20AM.png)

*iD in edit drop down on osm.org right now*

This pull request is a cleaned version of https://github.com/openstreetmap/openstreetmap-website/pull/261