Quantum 0.19.0

Added

Declarative schema (M6, DB-10). Keep a schema.sql with the tables as they should be; quantum migrate plan shows what changes against the migrations (new tables and columns, rebuilds that keep the rows, indexes), marks what loses data, and --write NAME saves the migration and its rollback after asking. Plans that lose data need --allow-data-loss. SQLite for now.
Change history (M22, DB-11). history: true on a datasource records every write an action makes — who, when, which action, the row before and after — in the same transaction; <ui:history table key datasource> lists a row's history in the browser and the console. projects/tarefas shows it on the edit page.