Enable random order of the integration tests

[php-coder]

http://robotframework.org/MavenPlugin/run-mojo.html#randomize

[php-coder]

When I enabled randomization of suite, all tests passed.

[php-coder]

With randomization mode all the following tests are failing:

• Create participant with blank required fields (the message: The text of element 'id=name.errors' should have been 'Value must not be empty', but it was 'Value is greater than allowable maximum of 50 characters')
• Create category with name in English (the message: The text of element 'id=msg-success' should have been 'Category has been added. Now you could proceed with creating series.', but it was 'Категория добавлена. Теперь вы можете создать серию.')

[php-coder]

Enabling random order for the tests that test for submitting a form with only required fields is tricky. In this case it's possible that the field is non-empty and contains a value from other test.