Add support for `%%` as label parameters

When using a translated text with parameters in the labels like %name% directly in the routing, i.e.

#routing.yml
# ...
    breadcrumb:
        label: 'My Product %name%'
# ...

the container tries to replace %name% with an actual container parameter, which is not desired.

This release adds support for label parameters with escaped %, like %%name%% (instead of %name%, by replacing %% in the template with % before translating.

Thanks to @Tobion for pointing to this possible solution.

This release also contains documentation updates and cleanups.