Apart from updating the SVG icons, the big icons have been added to
take advantage of the FA icons (and remove the old ones).
The icons.scss has been updated too, to display properly the big
icons.
We can use the Moodle language format for tour's name and description now.
Also, several existing bugs were fixed in this commit when we use
the Moodle language format for step's title and content.
Now, it will display the translated text in the breadcrumb, editing page
instead of displaying the [identifier][component]
Sara Arjona