MDL-38547 behat: New tests

Group mode icons are set to the correct
state when group mode is forced. According
to MDLQA-1597, MDLQA-1598,
MDLQA-1599, MDLQA-1600 and MDLQA-1601
MDL-38547 behat: New generic steps definitions

For advanced users as specified in the step
description, they can be used to match any locator
using any selector type
MDL-38486 behat: Course's topics highlighting steps definitions
MDL-38549 behat: New tests

Group mode activity icons toggle group
mode correctly. According to MDLQA-1603,
MDLQA-1604, MDLQA-1605, MDLQA-1606
and MDLQA-1607