API: Add ApiResult::META_KVP_MERGE

API: Add ApiResult::META_KVP_MERGE

This allows for merging the KVP key into the value for the alternative
output format. Specifically,

 { "key": { "foo": "bar" } }

can now be turned into

 [{ "name": "key", "foo": "bar" }]

instead of

 [{ "name": "key", "value": { "foo": "bar" } }]

Change-Id: Ie1f9235893dbbcd2948c46e0356360b5635a3ddd