Minor grammatical correction
Cookbook article about custom route loaders
Processed feedback by @lazyhammer and @WouterJ
Added use cases and explained the loader resolver
Added some references to bundles using route loaders
Wrap all yml strings containing "@" with quotes in order to render the
syntax highlighting correctly
Wrap all YAML strings starting with "@" with quotes

Without quotes, the parser doesn't render the syntax highlighting correctly
Issue #2378. Minor additions. Implemented suggestions by WouterJ.
Wrap all YAML parameter % uses with quotes

Without quotes, the parser doesn't render the syntax highlighting correctly
Remove useless spaces in the YAML code blocks
Reword sentence to make clear what should be read
Removed note, it's important information!
Add line information
Added some linebreaking
Moved text into a note
fix small typo - missing word
fix typo: form.name.label does not exist
Update the service container core symfony services tip

I felt the tip was a little clumsy. It appeared to be missing some
words and referenced the reader as if they were the person writing
the documentation.

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | none
Fix sentence
Add example server configuration

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | all
| Fixed tickets | #578 #1705