[WIP] Prod Error/Exception display fix

This removes the WebfactoryExceptionsBundle as it apparently conflicts with other parts of Symfony and caused a WSOD. It also creates an appropriate template override of the twig error template in order to remove the content outside of `<body></body>` so that the template displays within the zikula/smarty theme.

further work could include customizing the templates more and catching specific exceptions and doing something different.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #1789
| Refs tickets  | -
| License       | MIT
| Doc PR        | -
@cmfcmf and @Guite I think this is why the WSOD before. It was actually loading this template successfully but then choking on this line about the `WebfactoryExceptionsBundle:Exception:blocks.html.twig` because that wasn't loaded in `prod`