Update report's scrollview with better stability. closes #373

Improvements:
- A delay was added (ReportView.cs) before try a call to remote server. In case of fast scrolling, the delay will be canceled.
- The IsLoading state was updated. (SummaryReportsView.cs)
- A better method for calculate current report view. (InfiniteScrollView.cs) 

Fixes #373
Not sure the delay should be in the LoadData... it kind of is a UI domain problem. (ie the UI layer might implement a different way of accessing the view, then the 0.5sec delay would be very annoying)

maybe make the UI such that when scrolling has settled it calls LoadData()?