fix: InfinitScroll

Fix math of detecting when next set of entities to be shown:
1. Make sure if the screen is big and 1st page fit into it without
scroll, next page is displayed as well (previously scroll wouldn't
trigger since no scroll bar would be available)
2. Make sure to load next page without explicit scroll initiated by user
if entire 1st page already on the screen (applies to big screens)
3. Make next page load on fixed distance from the end (previously, the
more there are loaded records, the further from the end next page would
load, and this distance would increase with each page loaded, which
doesn't made any sense)