* [NOD-1320] Flush UTXOs to disk.
* [NOD-1320] Minor improvements and fixes.
* FullUTXOSet: change size type from int64 to uint64.
* Rename FullUTXOSet.size to FullUTXOSet.estimatedSize
* Fill NewFullUTXOSetFromContext with db context on virtual block
creation.
* Typo fixes.
* [NOD-1320] Stylystic fixes.
* [NOD-1320] Update tests. Improvements and fixes.
* Update blockdag/dag tests: prepare DB for tests.
* Update blockdag/utxoset tests: prepare DB for tests.
* Update blockdag/test_utils utils.
* Update blockdag/common tests.
* FullUTXOSet: remove embedded utxoCollection type. Rename
utxoCollection to utxoCache.
* Fix blockdag/block_utxo genesisPastUTXO func.
* Minor fixes and improvements.
* [NOD-1223] Delete unused files/packages.
* [NOD-1223] Move signal and limits to the os package.
* [NOD-1223] Put database and dbaccess into the db package.
* [NOD-1223] Fold the logs package into the logger package.
* [NOD-1223] Rename domainmessage to appmessage.
* [NOD-1223] Rename to/from DomainMessage to AppMessage.
* [NOD-1223] Move appmessage to the app packge.
* [NOD-1223] Move protocol to the app packge.
* [NOD-1223] Move the network package to the infrastructure packge.
* [NOD-1223] Rename cmd to executables.
* [NOD-1223] Fix go.doc in the logger package.
