* [NOD-1444] Implement getHeaders RPC command
* [NOD-1444] Fix tests and comments
* [NOD-1444] Fix error message
* [NOD-1444] Make GetHeaders propagate header serialization errors
* [NOD-1444] RLock the dag on GetHeaders
* [NOD-1444] Change the error field number to 1000
* [NOD-443] Immediately request missing parents in API server sync
* [NOD-443] Add rpc client log to api server
* [NOD-443] Fix wrong ordering of pendingHeaders queue
* [NOD-443] Fix error comparision at TestNewHashFromStr
* [NOD-443] Make a separate handleMissingParentHeaders function
* [NOD-443] Change log level
* [NOD-443] Put handleMissingParentHeaders next to handleBlockHeader
* [NOD-443] Make handleBlockAddedMsg function
* [NOD-443] Make reusable missingParentsHashesStr string
* [NOD-443] Remove redundant 's'
* [NOD-443] Refactor to first get all blocks and then add them to database
* [NOD-443] Rename variables and functions, and remove redundant logs
* [NOD-443] Make fetchBlockAndMissingAncestors use block hash as an argument
* [NOD-443] Add log only for first orphan block
* [NOD-443] Fix wrong order of adding blocks to pendingBlocks
* [NOD-443] Write logs for all orphans
* [NOD-443] Log only missing parents that are not already fetched
* [NOD-443] Rename rawVerboseBlockTuple -> rawVerboseBlock
* [NOD-443] Make fetchBlock return *rawVerboseBlock
* [NOD-443] Rename rawVerboseBlock -> rawAndVerboseBlock
* [NOD-164] Added validation routine
* [NOD-167] Extracted acceptedIDMerkleRoot calculation to its own method and implemented NextAcceptedIDMerkleRoot.
* [NOD-164] Fixed TestValidateFeeTransaction.
* [NOD-164] Fixed TestFinality.
* [NOD-164] Fixed blk_ tests.
* [NOD-164] Fixed if -> iff in a comment.
* [NOD-164] Minor style changes in comments.
* [NOD-164] Moved validateAcceptedIDMerkleRoot to before its population with the block's own transactions.
Replaced heavy call to verifyAndBuildUTXO in NextBlockFeeTransaction and NextAcceptedIDMerkleRoot with a call to pastUTXO on the virtual.
* [NOD-164] Fixed erroneous comment.
* [NOD-164] Inserted the logic from buildAndSortAcceptedTxs into calculateAcceptedIDMerkleRoot, since the former was meaningless on its own.
* [NOD-164] Changed looping over txsAcceptanceData instead of over node.blues.
