Merge pull request #89 from Wollac/wip/pow

packages/model/meta_transaction/constants.go

packages/model/meta_transaction/meta_transaction.go

packages/model/meta_transaction/meta_transaction_test.go

packages/model/value_transaction/constants.go

packages/model/value_transaction/value_transaction.go

packages/transactionspammer/transactionspammer.go

plugins/bundleprocessor/bundleprocessor_test.go

plugins/gossip/gossip.go

plugins/tangle/solidifier.go

plugins/tangle/solidifier_test.go

plugins/webapi-send-data/plugin.go