Add show-specific page for Admins, with tabs

[robmcl4]

Adds /show/:id?tab={1,2,3} to the Admin interface, with three tabs 'Details', 'Submissions', and 'Judge'

[robmcl4]

NOTE: in the story it's specified that we manage tab navigation by path, but I used the query-string

[billdybas]

This is way overkill and could be done just with React Router.

Use this directly or for inspiration: https://github.com/chacestew/react-router-tabs

And structure the URLs how the story says to.

[robmcl4]

Rewrote to use react-router-tabs in ed72791