Introducing ledger shards and new ledger syncing logic. (#247)

- The ledgers are stored in a sqlite database in ledger file system.
- Ledgers are organized in shards inside primary folder.
- Raw inputs are saved as shards inside blob folder. No input files are created if neither inputs nor outputs are available.
- Both last primary shard hash and last blob shard hashes are subjected to consensus and necessary sync operations are performed if out of sync.
- Hpfs sync support setting single sync targets from both ends of the list. (Targets set from front are prioritized).
- Contract and ledger syncs and serving are performed independently.

src/main.cpp

@@ -12,8 +12,7 @@
 #include "usr/read_req.hpp"
 #include "p2p/p2p.hpp"
 #include "consensus.hpp"
-#include "ledger.hpp"
-#include "ledger/ledger_sample.hpp"
+#include "ledger/ledger.hpp"
 #include "unl.hpp"
 
 /**
@@ -71,7 +70,6 @@ void deinit()
     p2p::deinit();
     read_req::deinit();
     consensus::deinit();
-    ledger::ledger_sample::deinit(); // Deinit method in new ledger implementation.
     sc::deinit();
     ledger::deinit();
     conf::deinit();
@@ -197,7 +195,6 @@ int main(int argc, char **argv)
                 LOG_INFO << "Contract: " << conf::cfg.contract.id << " (" << conf::cfg.contract.version << ")";
 
                 if (sc::init() == -1 ||
-                    ledger::ledger_sample::init() == -1 || // Init method of new ledger implementaiton.
                     ledger::init() == -1 ||
                     unl::init() == -1 ||
                     consensus::init() == -1 ||