Non view.getType() solution for ViewPool

[ypresto]

Currently ViewPool uses view.getClass() so all root views should have different classes.
This does not good if you want to use view types with same layout, like RelativeLayout.

I found it silently does not reuse view if no matching type is registered.
https://github.com/Comcast/FreeFlow/blob/master/FreeFlow/src/com/comcast/freeflow/core/ViewPool.java#L38
This caused performance issue on our app for long time...

I think it is more convenient if it has interface similar to ListAdapter#getItemViewType(int).
SectionedAdapter#getItemViewType(FreeFlowItem) or view.getTag(FREE_FLOW_VIEW_TYPE) is also convenient.