Port integration tests to Robot Framework

[php-coder]

After couple attempts to port all integration tests to Thucydides/Serenity/Cucumber-JVM (see #18) I concluded that:

• all work should be merged into the master as fast as possible
• probably we shouldn't use only one framework for all integration tests (but we will)

Based on this, the current view is to port most of the integration tests to Robot Framework (because the tests are easy to write) and port another portion of tests to Cucumber-JVM (later we'll be able to compare them). (no, we don't want to maintain 2 frameworks for the same purpose: #1019)

Plan

Port the existing tests

• port WhenAdminAddCategory
• port WhenAnonymousUserAddCategory
• port WhenAnonymousUserOpenNotExistingCategoryPage
• port WhenAdminAddCountry
• port WhenAnonymousUserAddCountry
• port WhenAnonymousUserOpenNotExistingCountryPage
• port WhenAdminAddSeries
• port WhenAnonymousUserAddSeries
• port WhenAnonymousUserOpenNotExistingSeriesPage
• port WhenAdminAtIndexPage
• port WhenAnonymousUserActivateAccount
• port WhenAnonymousUserAtForbiddenPage
• port WhenAnonymousUserAtIndexPage
• port WhenAnonymousUserAuthenticates
• port WhenAnonymousUserOpenNotExistingCollectionPage
• port WhenAnonymousUserOpenNotExistingPage
• port WhenAnonymousUserOpenTogglzConsole
• port WhenAnonymousUserRegisterAccount (successfulMessageShouldBeShownAfterRegistration and emailWithActivationKeyShouldBeSentAfterRegistration) (depends on Mailgun: send e-mail via API #935)
• port WhenUserAddSeries
• port WhenUserAtActivateAccountPage
• port WhenUserAtAuthPage
• port WhenUserAtIndexPage
• port WhenUserAtRegisterAccountPage
• port WhenUserLogsOut
• port WhenUserOpenTogglzConsole

Other work

• Integrate robotframework-lint
• Document how to use RobotFramework (will be solved in Document how to write integration tests on Robot Framework #1021)
• Add link to wiki page to the Dangerfile
• Update NEWS.txt
• Update README.md
• look for leftovers (git grep When)
• remove testng/fest-assert from everywhere (Dangerfile, README.md, testng.xml, checkstyle-suppressions.xml, etc)
• Close Port integration tests to Cucumber-jvm #18 and do cleanup
• deal with Port integration tests to Robot Framework #530 (comment)

[php-coder]

Improvements for tests:

• Create category with name in English: verify that after changing language, header will be in English
• Create category with name in English and Russian: verify that after changing language, header will be in Russian
• category/creation/{logic,validation}: log in as user (instead of admin)
• re-apply shouldHaveTitle to the index page
• re-apply shouldHaveUserBar to the index page
• re-apply shouldHaveContentArea to the index page
• re-apply shouldHaveLogo to the index page
• re-apply shouldHaveFooter to the index page

UPDATE(26.05.2019): most of them seem no needed now.