Like Sprint, this function converts the value of E into a string. If
the string has fewer than N characters, then spaces are added to the
front to make the length N.
Example
/**/ L := [1,2,3];
/**/ M := Format(L,20);
/**/ M;
[1, 2, 3]
/**/ Type(L);
LIST
/**/ Type(M);
STRING
/**/ Format(L,2); -- "Format" does not truncate
[1, 2, 3]