Reduce precision of coordinates to ~1m

[slowe]

I've truncated coordinates in the GeoJSON for Local Authorities and Wards to 5 decimal places - this is equivalent to ~1.1m at the equator or sub-metre resolution at the latitude of the UK. Given that these are simplified shapes anyway, they could be truncated even further.

I've also removed some white space in the coordinates to shrink the files even more.

The result is that the Local Authority GeoJSON is now 1.3MB (previously 2.6MB) and Wards are now 5.3MB (previously 8.6MB).

You could further strip out some of the properties of the areas if they are unnecessary e.g. in Wards removing properties "BNG_E", "BNG_N", "LONG", "LAT", "Shape__Are", and "Shape__Len would save a further 1MB.

[slowe]

Given the existence of previous versions of each GeoJSON I saved these truncated versions with new filenames rather than over-write the existing ones.