Adds a category to the course categories.
ADD CATEGORY <categoryname> [IN <parentidentifier> [HAVING description: <description> idnumber: <idnumer> visible: <visible> ]
Minimal instruction:
ADD CATEGORY <rootcategoryname>
ADD CATEGORY Language courses HAVING idnumber: LANGUES visible: 1
ADD CATEGORY English IN idnumber:LANGUES HAVING description: Category of English courses idnumber: ANG visible: 1
Sets the current category identifier to the created category.