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/hplog.cpp

@@ -72,7 +72,7 @@ namespace hplog
 
         const std::string trace_file = conf::ctx.log_dir + "/hp.log";
         static plog::RollingFileAppender<plog_formatter> fileAppender(trace_file.c_str(), conf::cfg.log.max_mbytes_per_file * 1024 * 1024, conf::cfg.log.max_file_count);
-        static plog::ConsoleAppender<plog_formatter> consoleAppender;
+        static plog::ColorConsoleAppender<plog_formatter> consoleAppender;
 
         plog::Logger<0> &logger = plog::init(level);