embedded permissions ui

[ghost]

Related to #11, display a ui to manage permissions for embedded iframe maps.

• allow once
• allow all from this domain
• reject once
• always reject from this domain
• allow/reject for X amount of time

Managing access should be per-dataset. Right now there is only planet-osm data but later there will be more.

Perhaps also:

• allow/deny custom styles set by the parent web app
• allow/deny custom fonts set by the parent web app

If you don't like how a web page displays a map or the font is too small or too large, you as a user should be allowed to override as much as possible.