[Tests] Some improvements for test suite

[phansys]

Q	A
Branch	master
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	n/a
License	MIT
Doc PR	n/a

TODO:

• Move "SYMFONY_DEPRECATIONS_HELPER" environment variable to phpunit.xml.dist;
• Add dev requirement for "ext-pdo_sqlite";
• Configure "framework.translator" explicitly;
• Use semver in for "SYMFONY_VERSION" at .travis.yml;
• Add tests for parameters created by HackzillaTicketExtension;
• Replace deprecated dependency "sllh/php-cs-fixer-styleci-bridge" with "friendsofphp/php-cs-fixer";
• Make public "hackzilla_ticket.user_manager" and "hackzilla_ticket.ticket_manager" services;
• Apply CS-Fixer for whole codebase.