MB-8531: Implement initial spatial index build

The initial index build for spatial indexes is now using the
new C code.

Change-Id: I8edd00cfb5341907369b468da6a9aca4ed13c21c
Reviewed-on: http://review.couchbase.org/27220
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>