Bid increments

[iragm]

Bids should increase by some percent, so that you can't bid 1001 on an item with a bid of 1000. This should be pretty easy to do in consumers.py, just need to figure out what the best increment is.

Request is:

Typicly $10 up to $500, $25 $500-$1000 and $50 over $1000.

I should see what ebay and shopgoodwill use.