Address suggestions for what has been typed into Street address

Relays Google Places Autocomplete (New); the key stays on the server. At most five street addresses, premises or roads -- no businesses or cities -- in lang (one of the app's fifteen, English otherwise), and only inside region when it is given. sessionToken is the client's, minted when typing starts and sent again on the details call for the suggestion picked, so Google bills the whole lookup as one session. With kind=place (the entry editor's "Find on map") nothing is narrowed by type: businesses, stations and landmarks are offered too. With both nearLat and nearLng (#1711), places within about 20 km of that position are preferred, without excluding the rest. Limited per user (120 an hour).