Pick last year in one click

The date-range picker has a new Last year preset, between Year to date and Last 12 months. It selects the previous calendar year, 1 January to 31 December. It's on every picker that shares the preset list: the reports, the Conversations list, the audit log, and a widget's Performance tab.

Conversations are kept for 12 months, so on the reports built from them (Overview, Insights, Quality, and the Conversations list) last year is always partial and a notice names the cutoff date.