[Geojson] Three more things...

[Martin Daly]

1) Add a *requirement* that features must have either exactly the same  
CRS as their parent featureCollection, or none at all. the latter  
implying using the featureCollection CRS (where present)

2) Add a *recommendation* that date properties are encoded by  
producers as ISO8601 strings, and parsed back into dates by clients  
(where possible)

3) Add a *recommendation* that all features in a featureCollection  
share the same set of properties (different values of course), to fit  
into the near-universal relational model

Comments?

M