Refactoring: replace 'classes' with 'icon-class'
The array-based link definitions are derived from BaseTemplate.
They normally consist of the fields text, title, href, class and id.
A lot of work is done with icons that do not belong to the link element,
but are rendered in a separate element (i or span), therefore
a corresponding icon class is used.
This was previously solved using the field 'classes'.
Since this name is not very meaningful it is changed to 'icon-class'
Pls Cherrypick to REL1_31