Implement dashboards as web components

/-/ddd/dashboard/* is now a collection of web components in typescript.

www/static/DashboardApp.ts is the entry point and the main controller of the dashboard UI. The other major parts are:

• the chart widget is in vega-tonic.ts
• the search form / filter interface is in filter-input.ts

Other significant changes:

• Move charts to separate yaml files and queries to separate sql files -- Instead of everything in one big yaml file --- move the definition of each chart into www/templates/views/charts/*.yaml --- "canned queries" are now in www/sql/*.sql --- Dashboards and tabs are still defined in www/metadata.yaml

Plus some other smaller fixes:

• Make phid links work with base_url in datasette
• fixup ci & deployment issues in .gitlab-ci.yaml
• Fix the metrics mapper cli tool to properly handle cursors. Now it can automatically resume importing at the point where the previous run left off.