Refactored and Fix list sort arrows
Support for class-level validation

This allows for

    $errorElement->addConstraint(new UniqueEntity(['fields' => 'email']));

and similar code without an enclosing ->with().
don't show 'first' when link is same as 'previous' button

figured later i should have fixed the 'first' button as well, no point in showing it when the back button points to the same page.
Added support for setting group translation_domain

- Ability to set translation_domain on a form group
- Translation domain cascades to group fields
- Added unit test for FormMapper
- Extended AdminInterface to have [get|set]FormGroups
Updated doc
Merge pull request #1378 from dantleech/ext_trans_domain_cascade

Added support for setting group translation_domain
Fix bug in getTemplate method
Added unit tests, added show_currency and show_percent template
Merge pull request #1383 from pulzarraider/admin_extension_fix

Fix for bug in getTemplate in SonataAdminExtension
Update preview mode
Fix falling unit tests in SonataAdminExtensionTest
Merge pull request #1385 from pulzarraider/timezone_unittest_fix

Fix falling unit tests in SonataAdminExtensionTest
Fix NativeLabelTranslatorStrategy whitespace bug
Update composer.json
Merge pull request #1384 from EmmanuelVella/preview

Update preview mode
Merge pull request #1386 from pulzarraider/native_label_translator_fix

Fix NativeLabelTranslatorStrategy whitespace bug
Merge pull request #1367 from sjopet/patch-5

don't show 'first' when link is same as 'previous' button
[translation][ja] add missing Japanese translation
[translation][ja] tweaks for Japanese translation
custom date and datetime formats in list