Refactor progress fraction calculations. Re-add function for calculating topic progress fractions.
Refactor progress fraction calculations.
Re-add function for calculating topic progress fractions.

indirectlylit/kolibri,learningequality/kolibri,learningequality/kolibri,mrpau/kolibri,christianmemije/kolibri,rtibbles/kolibri,christianmemije/kolibri,indirectlylit/kolibri,benjaoming/kolibri,rtibbles/kolibri,jonboiser/kolibri,DXCanas/kolibri,lyw07/kolibri,jonboiser/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,MingDai/kolibri,benjaoming/kolibri,mrpau/kolibri,lyw07/kolibri,learningequality/kolibri,lyw07/kolibri,benjaoming/kolibri,jonboiser/kolibri,rtibbles/kolibri,mrpau/kolibri,lyw07/kolibri,DXCanas/kolibri,DXCanas/kolibri,jonboiser/kolibri,mrpau/kolibri,DXCanas/kolibri,learningequality/kolibri,rtibbles/kolibri,MingDai/kolibri,MingDai/kolibri,christianmemije/kolibri,benjaoming/kolibri,christianmemije/kolibri,MingDai/kolibri