Memory window fixes

* Fix for Issue #15 to scroll to top of memory window when loading new
items. Sadly, this requires reflection to scroll a virtualized items
control in WPF.
* Fix for Issue #16. The memory window now displays 16 bytes rather than
8
* Slightly better fix for Issue #13
* Fixed bug in PagedList where some internal fields weren't cleared when
the items were cleared, resulting in some inconsistent state.