core: initial commit for logger (#228)

* Replace "log.*" with logger.
* Add simple logger to log with log package.
* Add debug logs to all calls to these interfaces:
   - core.Application
   - core.Governance
   - core.Network
* Add Stringer to these types:
   - types.DKGComplaint
   - types.AgreementResult
   - types.DKGMasterPublicKey
   - types.DKGFinalize

1 files changed, 2 insertions, 1 deletions

diff --git a/integration_test/node.go b/integration_test/node.go
index 09d1557..b6704e8 100644
--- a/integration_test/node.go
+++ b/integration_test/node.go
@@ -121,7 +121,8 @@ func NewNode(
 			core.NewAuthenticator(privateKey),
 			app,
 			app,
-			db),
+			db,
+			&common.NullLogger{}),
 	}
 }