Allow dev-like errors in production

For example for uniregtest. In the ENV, set
“DISPLAY_PRODUCTION_ERRORS=true”.
Add event age range. (Admin half.)
Better website title

It’s really confusing having multiple instance of the app open. This
makes the page title more relevant.
Add validation for event age range on sign-up
Attempt at: limit displayed event catagories to those allowed for registrants age