We need to create a job running tests using multirepository setup (with multiple databases).

Idea:

• create a Behat feature/Symfony command that sets up a mutlirepository configuration, where the default database connection is broken (that way anything that tries to use it will immediately break). Example config: https://github.com/ezsystems/ezplatform-workflow/pull/98#pullrequestreview-326145831
• add it to Travis to execute before composer ezplatform-install during setup
• rework bin/console so that siteaccess can be passed not only by --siteaccess option, but also through ENV variable (so that we can keep using { {composer ezplatform-install}

  .

• execute AdminUI or PageBuilder tests - tests with broad coverage