Remove site key input from search page

[Alan Noble]

The search page is the only page that allows the user to enter the site key manually, which is unwieldy and error prone. Every other page uses the site key that was selected by the home-page site selector (which will eventually feature on all pages).

[Alan Noble]

Implemented in https://bitbucket.org/ausocean/vidgrind/commits/7af091029681fbfc89511b75f3c6d8b9a66be8b8