Alternative formatting on freebsd/developer/* blocks

Use angle brackets instead of italic to denote mandatory fields after
"freebsd/developer/" blocks. "freefall name" and "NickServ name" are
also renamed to "freefall username"` and "FreeNode account".

Reviewed by: debdrup, ygy, lwhsu
Approved by: philip (mentor)
Differential Revision: https://reviews.freebsd.org/D29285