Make the command-line usage message more clear
Switch from using the remote Overpass API server to osm3s_query locally

The KML generation scripts for MapIt Global used to make a huge number
of queries to http://www.overpass-api.de/api/interpreter - this is
slow and hits their service rather hard.  Setting up a local server
and running queries using the osm3s_query binary is obviously a great
deal faster, and doesn't put large load on an external service.
doctests: any ID is fine, it doesn't have to be hexadecimal
doctests: Scotland now has 71 members in the relation
Ignore missing elements when trying to join ways

Sometimes the API returns an element which is missing - the
code marks such a way as missing, but it will still be
passed to join_way_soup.  Ignore such elements.
doctests: make sure the parser's using an empty cache
Deal with empty results being returned from the API

Previously exceptions would be thrown if the API return an
empty XML file when trying to fetch an element.  This does
sometimes happen, so this commit changes the behaviour so
that such missing elements are ignored.
doctests: add an extra tag that South Cambridgeshire now has
Remove the get-boundaries-from-planet.py script

It turns out that iteratively parsing the planet.osm file is
too slow to be workable, and using a local Overpass server
is much preferable.
Make normalize_whitespace usable again

The calls to self.normalize_whitespace fail at the moment
with the error:

  TypeError: normalize_whitespace() takes exactly 1 argument (2 given)

We could just add self as the first argument to
self.normalize_whitespace, but since this method isn't
dependent on self, we might as well make it a static
method.
Remove an unnecessary level of indentation
We should exclude polygons with <= 3 points, not < 3

This error would cause KML files to be generated with
invalid polygons (e.g. A -> B -> A)
Add a script for timing point -> areas lookups in MapIt UK

This script generates random-enough locations in the UK
and uses the timeit module to time Area.objects.by_location
lookups for those locations.  This is useful to assess how
the performance of MapIt UK would be affected by adding
polygons of various sizes and complexities to an existing
instance.

This script was written with Jenny Duckett.
Fix an error with an initial Boundary-Line import without --commit

Thanks to Geoff Stockham for pointing out this problem.  This
fixes issue #48.

When we see a second polygon with the same unit_id and this
is a new import, a dry-run import will fail because the name
can't be found in the database from the unit_id - it was never
saved the first time around.  As with finding the name from
ons_code we should ignore this error if we're not saving to the
database.

(The example in the bug report is the second polygon in
Waterbeach ED in county_electoral_division_region.shp.)
Correct a test for polygons with too few points

Thanks to Jenny Duckett for pointing this error.  In fact, this
corrected version of the test is too brutal - we ignore the file
if any Polygon in the MultiPolygon has too few points.  In a
subsequent commit I will change this behaviour.
Remove an old script (no longer used) to avoid confusion
Make save_polygons ignore any polygon with less than 4 points
Specify no-location parameter correctly for Crown Dependency postcodes.
Add fixture of some special postcodes.
Add script to add old ONS codes to a database containing only the new GSS ones.