Add optional debug logging for indexer

adds a command line parameter to indexer(debugLog) to enable debug logging
When debugLog is enabled, all database insert/read/scan query will be logged
Persist sequence vector for all indexes

After persist interval is over, persist sequence vector for all indexes
This makes sequence vector persistence global rather than index based
Add command line option to specify indexer node

Indexer node can now be specified as a command line argument
while starting index manager
Drop index should fail if indexer is not running

Index Manager should return fail if indexer cannot service the drop
index request. Fixed a bug here which was preventing this from happening.
bug fix for indexer init in index_manager