Bump to v3.0.0

Merge branch 'master' of github.com:input-output-hk/mantis into release/v3.0.0

1. Command executed (from develop)
	git pull -X ours origin master
2. Manual deletes:
	.circleci/config.yml
	src/it/scala/io/iohk/ethereum/SimulateTransactionTest/SimulateTransactionTest.scala
	src/main/scala/io/iohk/ethereum/mining/BlockGenerator.scala
	src/test/scala/io/iohk/ethereum/mining/BlockGeneratorSpec.scala

3. Remove all the incoming changes from master

Author: mirkoAlic