Bookmarks for center/zoom of a map

[ThomasHalwax]

When drawing symbols on a map users often switch between different centers and zoom levels. I'll call the tuple of center and zoom level a 'bookmark'. In order to return to a previously used bookmark or to switch between bookmarks we should provide a way to

• persist the current center/zoom level and specify a name for this bookmark
• enumerate/list all persisted bookmarks and
  • move the map to the selected center/zoom level
  • rename an existing bookmark
  • delete an existing bookmark

When a user selects a bookmark we could use a smooth animation (like 'fly to') to move the map to the given center/zoom.

Bookmarks should be project-related and should not change basemaps and layers.