LDEV-3962 Similar changes done to Open Lesson dialog as previously done to Open/Save sequence in authoring * ability to save sequences on pressing the Enter button when title input is focused * focus title input field in case this element is visible in the current viewport (to avoid unwanted scrolling) * ability to start lessons on double click * prevent sequences from being deselected on any subsequent clicks * Make 'Tour' word to appear after icon in order to be consistent with the rest of the buttons * Make #notificationsPendingCount to be less prominent in case there are no messages. And assign it 'btn-primary' class when there are some messages available