Don't double count question boost

[SylvainChevalier]

Problem

Currently:

• Here we set the boost to +20.
• Here we multiply it by 20.

So when an admin clicks "boost" it increases the activity by +400, equivalent to 40 comments.

Solution

Either store the boosts as +1, or don't multiply them by 20. I lean storing them as +1 since that leaves all the weights in the same place.

Also let's make the boost +50, equivalent to 5 comments. Less clicking for admins.