Aggressive reusing of views in reports. Closes #428

All of the views (both fragment and list view) are pooled and reused now. It creates a slight lag spike when entering the reports view (pre-inflating all of those views), but after that there are no more inflations when navigating reports, thus less dropped animation frames :)

As an added bonus, made zoom level switching a bit more natural, by reseting the date period being shown to today when switching.

Closes #428