Node improvements (#47)

* block partial persist

* replaced refactored files with old one.

* removed gokit/log from deps

* Tweaks to not overburden remote nodes with getheaders/getblocks

* Changed Transporter interface to not take the server as argument due to a cause of race warning from the compiler

* started server test suite

* more test + return errors from message handlers

* removed --race from build

* Little improvements.

pkg/core/blockchain_test.go

@@ -76,6 +76,5 @@ func TestAddBlock(t *testing.T) {
 func newTestBC() *Blockchain {
 	startHash, _ := util.Uint256DecodeString("a")
 	bc := NewBlockchain(NewMemoryStore(), startHash)
-	bc.verifyBlocks = false
 	return bc
 }