Complete bridge authors export: add Institution and Country

I also reordered the export to group the participations by author.
Add computation of working group participation ratios

The subquery was copied from:
ipcc-acquire/question03/compute-working-group-membership-ratios.sql

It was renamed from `bridge_participations` to `bridge_wg_ratios`.
Add columns with ratios of Working Group participations
Convert WG number (1,2,3) to text (WG I, WG II, WG III)
Rename columns `Chapter` to `Chapter #`
Add column with participation role (symbol)
Add subquery to compute role ratios

The subquery was copied from:
ipcc-acquire/question05/compute-role-ratios.sql

and renamed from `ratios` to `role_ratios`.
Add columns with ratios of participation in different roles