Memory leak in MVVM binding

Hi.

We use ZK framework in production and we identified severe memory leaks in MVVM binding.

I made example, It's available on link https://github.com/samuelbr/zk-mvvm-memoryleak.

Steps to reproduce:
1. Deploy application.
2. Click multiple times on a button
3. A lebel with a number above the button is count of components in the TrackerImpl component map.

Memory leak is caused by rising number of components in the TrackerImpl field _compMap. Potentional problem is in a combination of using a ListModelList methods (add, clear) and using ZK postNotifyChange annotation (or similar method in BindUtils class).