https://jira.hyperledger.org/browse/FAB-1664



This changeset:
- Renames package ledger/util/db to ledger/util/leveldbhelper
- Implements a leveldb provider
  (that enables using same leveldb instance as a multiple logical dbs)
  in util package for being able to reuse across statedb, index,
  and later for historydb
- Implements a provider as a single point of invocation
  for managing multiple block storage
- Uses a single leveldb instance for block storage index
- Makes the structures other than providers as private
  to their respective packages

Change-Id: I5f0b3b9aa8ef3ac1ccdce4f3c6fa6d842b5318c1
Signed-off-by: manish <manish.sethi@gmail.com>

https://jira.hyperledger.org/browse/FAB-1201



Change-Id: I34f7f56887c25dae712188a50e8bdcd13ae619d2
Signed-off-by: manish <manish.sethi@gmail.com>

https://jira.hyperledger.org/browse/FAB-1035



Just a reorg of the files in keeping with creation of
"common" and "orderer" package files with corresponding
import changes.

A final cleanup of removing unused messages and renaming
"2" suffixed protos needs to be done as a final cleanup

Change-Id: I81cfa970ca5b4ff668dd70247117bd4e34548ad5
Signed-off-by: Srinivasan Muralidharan <muralisr@us.ibm.com>

Raw ledger provides basic functionality for storing and
retrieving blocks. This is intended to be used by an orderer service
https://jira.hyperledger.org/browse/FAB-56



Change-Id: I3fb733f5be53b6f630c20554ba4e362540b8f55a
Signed-off-by: manish <manish.sethi@gmail.com>