Merge dashboards

[hughjonesd]

We have two shiny dashboards: uj-dashboard and DataExplorer. Other things being equal, we should only have one. Both do roughly similar things.

In future, we might want different dashboards, e.g. one for management and one for external users. But management may be better off doing stuff in Coda which doesn't require R programming expertise.

(Actually, if we could expose stuff in coda to the public, that might also be good.)

This needs management discussion so we can work out the content and goals of the dashboard.

[hughjonesd]

See also #15.