boilerplate for scenario3
select X axis
select Y axis
test scaffolding for available years
filter available years for selected indicators
save year selection
pre-select current filters
deselect year if new value is not available
display filters on scenario3
move metadata title to parent template
metadata view: arbitrary field name in model
show metadata boxes for scenario3
Merge branch 'scenario3-filters'
extract index_by to App namespace
refactor Scenario1FiltersView.render
extract Scenario1FiltersView.get_options method
refactor Scenario1FiltersView.update_filters
Merge branch 'refactor-scenario1-filters'