Define some constants for transforms
Define some constants for transforms

- Airy 1830 ellipsoid semi-major and semi-minor
- GRS80 ellipsoid semi-major and semi-minor
- Easting and Northing of True Origin

urschrei/rust_bng,urschrei/rust_bng,urschrei/lonlat_bng,urschrei/lonlat_bng,urschrei/lonlat_bng