This CR adds the following 6 chaincode APIs which enable chaincode
to acess/modify the partitioned private data. A collection name denotes
a partition. These will only be included in experimental builds.
1. GetPrivateData(collection, key)
2. PutPrivateData(collection, key, value)
3. DelPrivateData(collection, key)
4. GetPrivateDataByRange(collection, startKey, endKey)
5. GetPrivateDataByPartialCompositeKey(collection, objectType, []keys)
6. GetPrivateDataQueryResult(collection, query)

Changes have been made in both shim and peer side. For APIs 4 to 6,
ledger support is not added yet.

Enabled only TestQueries/TestQueriesPrivateData functions in
exectransaction_test.go to perform end-to-end test (chaincode
to ledger).  Earlier, all test functions in exectransaction_test.go
was disabled as it was taking a lot of time to execute.
Currently, TestQueries/TestQueriesPrivateData take less than
15 seconds and hence can be enabled for e2e testing

Also needed to modify core/chaincode/platforms/golang/platform.go
in order to support building chaincode with the experimental tag.

Change-Id: I6b026f0628c5c808776f05852c7910f60f4a99c4
Signed-off-by: senthil <cendhu@gmail.com>
Signed-off-by: David Enyeart <enyeart@us.ibm.com>
Signed-off-by: Gari Singh <gari.r.singh@gmail.com>