Fix for #122

#122 : Budget source bug

When clicking on a bubble, search if donors & donors_countries contains the processed facet, and if it doesn't default to UNDP Regular resources.

This is because we add UNDP Regular Resources bubbles for core donors; core donors can be countries or budget sources. When clicking on a bubble we were only checking if the bubble donors contain the selection in the country filter (and not the budget source filter). 

cc @smit1678