…ts and Range (webmozart)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[Validator] Added date support to comparison constraints and Range

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #3640, #7766, #9164, #9390, #8300
| License       | MIT
| Doc PR        | symfony/symfony-docs#4143

This commit adds frequently requested functionality to compare dates. Since the `DateTime` constructor is very flexible, you can do many fancy things now such as:

```php
/**
 * Only accept requests that start in at least an hour.
 * @Assert\GreaterThanOrEqual("+1 hours")
 */
private $date;

/**
 * Same as before.
 * @Assert\Range(min = "+1 hours")
 */
private $date;

/**
 * Only accept dates in the current year.
 * @Assert\Range(min = "first day of January", max = "first day of January next year")
 */
private $date;

/**
 * Timezones are supported.
 * @Assert\Range(min = "first day of January UTC", max = "first day of January next year UTC")
 */
private $date;
```

Commits
-------

60a5863 [Validator] Added date support to comparison constraints and Range

…mparison constraints and Range (webmozart, javiereguiluz)

This PR was submitted for the 2.7 branch but it was merged into the 2.6 branch instead (closes #5384).

Discussion
----------

Added information about the new date handling in the comparison constraints and Range

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes (symfony/symfony#11673)
| Applies to    | 2.6+
| Fixed tickets | -

This PR finishes #4143

Commits
-------

b6c1a93 Added the "payload" option back
7ef2e6a Show annotations first
e3efbbf Reordered the code blocks to show Annotations, YAML, XML and PHP
39f46e1 Fixed the issues reported by @xabbuh
7003445 Finished the documentation of the new data comparison validators
1fa69fe Added information about the new date handling in the comparison constraints and Range