Moved text into a note
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
Merge pull request #2444 from WouterJ/doctrine_add_note

Moved text into a note in book/doctrine
fix grammar mistake
Merge pull request #2452 from havvg/patch-3

fix typo: form.name.label does not exist
typo
Merge pull request #2467 from colindecarlo/service-container-update-core-symfony-services-tip

Update the service container core symfony services tip
update doc for yaml format for null

I found that ~ is used for null instead of -
Merge pull request #2482 from andreia/fix-01

Fix sentence
Merge remote-tracking branch 'origin/2.0' into 2.0
Fix upload code
[#2454] Manually adding changes that wouldn't patch cleanly to 2.0
Merge branch '2.0' into 2.1