Fix error when deleting a triangle vertex

Fixes #1712
Fix close button event binding in save dialog

Fixes #1713
Change delete shortcut to ⌘⌫/Ctrl-Backspace

Refs #1698
Refine toilet preset

Fixes #1697
Remove maximization

This is low utility now that iD is full-width when
embedded, and the key combination conflicts with "Move".

Fixes #1482
Remove unused
Refactor BackgroundSource
Add default "Locator Overlay" layer

A layer that is by default visible at <z16 and can
orient you with major roads, cities, borders, etc.

Fixes #1301
Fix unsupported message (fixes #1720)
Add help topic on relations

Fixes #1708
Fix tests
Default wildcard tags to "yes"

Fixes #1715
Reduce prominence of share links, add G+
Add Knight.
Update README.md
Add terms for tourism=artwork (mural, sculpture, statue)
Merge pull request #1726 from ajashton/artwork-terms

Add terms for tourism=artwork (mural, sculpture, statue)
Add Ranger Station preset
Exclude Locator Overlay from imagery_used
Fix preset list header text after deleting search value

Fixes #1725