Represents the scenarios from the Spreadsheet Document.
-Booking stores in the data store a Date object and GeoPt(latitude,
longitude) objects. Previous implementation for latitide, longitude,
start_date_ms, end_date_ms has not been removed.

-Corner Case Bug remaining:
--(1/2) Making a Booking with both start_date & end_date between the
range of (start_date, end_date) of an existing Booking
--(2/2) Sequence of Bookings may remain conflcit free.

the ajax request with (start_time, end_time) from find_spot now supplies
(start_time, end_time -1).
-Other Bug fixes & Cleanup.