[Refactor] Move smooth scrolling code to a new module, and use that for page (i.e. non-CU) scrolling (in mod_basicPagUtils) as well.
[Refactor] Minor refactoring - Changed array names $CUsArr to CUsArr and $CUs to CUs
[Perf] set/update $commonCUsAncestor only when filtering is invoked, instead of doing it each time CUs are updated