Add commenting to Videos

[theCatsPaw]

So, there are 2 common commenting systems. The tree based structure(that reddit has), and the flat structure (same as the BitVid forums). We're atm unsure which is a better fit, implement both in a compatible way to allow the user to switch.

Tree based:

• top level sorted by date, newest at top
• second level+deeper, sorted by votes

flat based:

• sorted by date, newest at top