Fix various documentation bugs

Fix certain type of bonus can actually trigger with weapon skills
http://hercules.ws/board/tracker/issue-7897-bug-or-bad-description/
Fix duplicate sample typo
http://hercules.ws/board/tracker/issue-4984-wrong-test-duplicate-npc-sample/
skill script command doesn't has type 4
http://hercules.ws/board/tracker/issue-7565-skill-script-command-invalid-flag/