Move stats api types into api/types package
Move stats api types into api/types package

Move the stats structs from the api/stats package into a new package
api/types that will contain all the api structs for docker's api request
and responses.

Signed-off-by: Michael Crosby <951f4c7b5d47e32d0112c78d14a98eaa23e6b5ef@gmail.com>

thaJeztah/engine-api,docker/engine-api,msabansal/engine-api,rhatdan/engine-api,mikedougherty/engine-api,vdemeester/engine-api,jwhonce/engine-api