REST: Explicitly define fields

REST: Explicitly define fields

Explicitly define included fields (using 'Meta.fields') rather than
those that should be excluded (using 'Meta.exclude'). This ensure fields
that are exposed by the API don't change unless we explicitly change
them

The only side-effect of this change should be a consistent ordering of
the output - the ordering used in the 'Meta.fields' will be consistently
used, thus ordering is now important and some fields are moved around
to reflect this.

Signed-off-by: Stephen Finucane <stephen@that.guru>
Reviewed-by: Andy Doan <andy.doan@linaro.org>