Handle changes in ContentTypes more gracefully.

[bobdenotter]

When adding a new contenttype foo_bar_qux, you might get this error when requiesting a page:

Twig\Error\RuntimeError:
An exception has been thrown during the rendering of a template ("Parameter "contentTypeSlug" for route "listing" must match "homepage|pages|entries|blocks|page|entry|block" ("foo_bar_qux" given) to generate a corresponding URL.").

It's remedied bu running bin/console cache:clear, but this is not very user friendly.

[I-Valchev]

Two more things:

• View saved version on site button does not work before clearing the cache
• Adding a CT which does not have a singular_name or singular_slug gives a 500, which is difficult to debug.

[I-Valchev]

Update on this:

container params can only be set before the container is compiled, which means we cannot update the container bolt.requirement.contenttypes param at runtime. That means when a new content type is created, cache has to be cleared.

This looks, however, like an important usability issue impacting the "simplicity of creating content" aim of Bolt :/