remove TimeIotaMs from ABCI consensus params (#3403)

Also

- init substructures to avoid panic in pb2tm.ConsensusParams
Before: if csp.Block is nil and we later try to access/write to it,
we'll panic.
After: if csp.Block is nil and we later try to access/write to it,
there'll be no panic.

types/protobuf_test.go

@@ -65,6 +65,8 @@ func TestABCIConsensusParams(t *testing.T) {
 	cp := DefaultConsensusParams()
 	abciCP := TM2PB.ConsensusParams(cp)
 	cp2 := PB2TM.ConsensusParams(abciCP)
+	// TimeIotaMs is not exposed to the application.
+	cp2.Block.TimeIotaMs = cp.Block.TimeIotaMs
 
 	assert.Equal(t, *cp, cp2)
 }