So... Long story short, I killed Melka. I got frustrated because the gate said `Press E to Open Gate` and it simply would not. I gave up at the time (several actual days ago) and am just now going through my `Miscellaneous` quests to clean them out of my log. Today I walked up and saw, oh... there's a chain there. I opened the chain, and there was the body. 

Well apparently murdering her didn't invalidate the quest and now it's still in my log as `Kill the Hagraven Petra`. I'm on PC and honestly just want to get it out of my log. I consider the quest "complete" as my goal was to get a staff and after looting the body, uh mission accomplished. I'm fairly confident that this quest was purely optional (and that I took a valid course of action to complete it).

Is there a console command to complete a quest (or mark it as complete) or any other way of removing it from my log?