* [DEV-92] Covered blocknode.go with tests.
* [DEV-92] Added test for blockSet.highest. Fixed a bug in it.
* [DEV-92] Added tests for blockSet.subtract and blockSet.addSet.
* [DEV-92] Covered blockset.go with tests.
* [DEV-92] Got rid of some old stuff related to STXOs.
* [DEV-92] Covered error.go with tests.
* [DEV-92] Covered utxoSet with tests.
* [DEV-92] Fixed formatting.
* [DEV-303] Implement block finality
* [DEV-303] Add finality tests
* [DEV-303] Make finality tests use maybeAcceptBlock
* [DEV-303] Only check finality rules if we are fastAdd mode
* [DEV-303] replace hasBiggerFinalityScoreThan checks with .finalityScore()
* [DEV-301] implement blockNode.chainHeight as the height of the selected parent chain
* [DEV-301] add description to TestChainHeight
* [DEV-301] Delete comment on TestChainHeight and expalain about the dag
