refactor remove extra type define

So we are going to maintain this package?
This file needs to be refactored. I think we need to move the 
```go
subscriber struct {
	updateCh chan<- *SubStateUpdate
	errCh    chan<- error
	sync.Mutex
	ignore      map[dbus.ObjectPath]int64
	cleanIgnore int64
}
```
from dbus.go to subscriber.go. And attach all the functions in subscriber.go to `subscriber`.

I am trying to do this. But there are some dependencies issue to deal with.