Break down host spending further

[ChrisSchinnerl]

Right now we track all contract related spending on a per-host basis in the categories AccountUsage and TotalUsage.
When looking at the Spending Rate dashboard though, the difference between total and accounts is sometimes as large as 4x.
We should break it down further to see exactly what RPC we spend money on.

Checklist

• AppendSectors
• SectorRoots
• FreeSectors
• RefreshContract
• RenewContract
• ReplenishAccount (AccountUsage)
• Unspecified (no need for a db column, we can just compute total - the other categories on the fly)