Since this is an admin screen, we can show the exception message
unconditionally.

Fix that persistent would override other database options.

Closes: #1546

Remove references to defaultDictionary

Cleanup hooks

Hook 'metadata_hosted' and 'frontpage' are no longer called so do
not register hooks for them. Update the docs. Remove useless call
to configpage hook on admin module Test page (likely a copy-paste
error).

This was already the result after processing previously.

They were broken in master. The admin module now performs this
function. So to reduce duplication and to keep the metadata endpoints
simple, we remove the broken code here instead of fixing it.