big sections are ripe for division

here are some sections that have accumulated many items that might be numerous enough to make their own section. 3 or more items is enough to make a stand alone section

books/free-programming-books-subjects.md#misc books/free-programming-books-subjects.md#software-architecture books/free-programming-books-subjects.md#mathematics courses/free-programming-courses-subjects-en.md#misc