DOCS-641 geospatial review edits

Signed-off-by: Sam Kleinman <samk@10gen.com>
Minor: redundant term

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-1254 powerOf2 textindex and DOCS-1247 geoWithin in agg

Signed-off-by: Sam Kleinman <samk@10gen.com>