[2.3] Examples that points to the DataCollectorListener should be removed.
Reverted removal, removed API links instead
tweaks to the contribution chapter
Added information about float choice lists
feature #4241 [Form] Added information about float choice lists (peterrehm)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4241).

Discussion
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[Form] Added information about float choice lists

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | no
| Applies to    | all
| Fixed tickets | -

Added an information about the possibility to have a choice list with float values.

Relates to symfony/symfony#11849

Commits
-------

81e3728 Added information about float choice lists
minor #4245 [Contributing] tweaks to the contribution chapter (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Contributing] tweaks to the contribution chapter

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

Some tweaks for the changes made in #4223.

@javiereguiluz Sorry,  didn't find the time to review it in the first run.

Commits
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f4b0b8e tweaks to the contribution chapter
minor #4237 Finished #3886 (ahsio, WouterJ)

This PR was merged into the 2.3 branch.

Discussion
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Finished #3886

Replaces https://github.com/symfony/symfony-docs/pull/3886

Commits
-------

01057ae Reverted removal, removed API links instead
0670f25 [2.3] Examples that points to the DataCollectorListener should be removed.
Merge branch '2.3' into 2.4

* 2.3:
  Added information about float choice lists
  tweaks to the contribution chapter
  Reverted removal, removed API links instead
  [2.3] Examples that points to the DataCollectorListener should be removed.

Conflicts:
	components/form/form_events.rst