add request_hash/1 to riak_kv_vnode & export object_info/1

necessary to support resizing ring
make PR/PW account for forwarding during ring resizing
changes to aae to support ring resizing

* dont create trees initially when starting primaries in
a larger ring
* handle cases where exchange is enqueued for index that
exists in older, larger ring (after ring is shrunk)
dont forward gets during ring resizing

all writes are performed locally so no reason to add
extra network traffic
move bucket_nval_map/default_object_nval to core
nval_map/1 needs to be exported by vnode for ring resizing
Merge #530 into staging-1.4
adjust handling of non-existent index in entropy manager
fix call to riak_core_ring_manager:get_chash_bin/0