Refactored and Fix list sort arrows
Minor documentation fixes.
Support for class-level validation

This allows for

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

and similar code without an enclosing ->with().
added missing option 'label_catalogue' for dashboard groups in di configuration
added feature to wire extensions dynamically using configuration
enhance and update bulgarian translation
remove slugify filter in tab id generation

slugify function doesn't work correctly on Russian symbols, so we may use index of tab without name
Merge pull request #1354 from wiistriker/patch-1

remove slugify filter in tab id generation
Merge pull request #1353 from bmanolov/bg-translation

Enhance and update bulgarian translation
Merge pull request #1352 from sjopet/extensions

added feature to wire extensions dynamically using configuration
Merge pull request #1349 from virtualize/master

added missing option 'label_catalogue' for dashboard groups in di config
Merge pull request #1297 from pezia/master

Minor documentation fixes
added a link to the extensions.rst file in the toctree
added check to pager template to not show last-page button if its the same as next-page
Merge pull request #1357 from sjopet/sjopatch

fixed toctree in docs, added check to pager template
[documentation] Added description of Role Handler

There was a lot of doc about ACL, but (nearly) nothing about the role handler. So here is some precisions about it.
Commented about access_strategy
Updated slovak translations
Added ability to set translation domain on field description
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.