Add Automated Offer deviation control.

[DanielGurianov]

Add the option to set a negative deviation in the offered games count.

For exmaple:
I want to trade 6:1, but when matching the user cant take 6 games and can take only 5 out of the 6.
If I set 6 with deviation of 2, a user who can take a 5:1 and a 4:1 will still recieve and offer, while 3:1 and less would behave as currently without any offer created for them.

Why?
-Quality of life (self explained)

-Load on barter:
Instead of creating X offers to get the outcome (e.g. 6:1 then 5:1 then 4:1) create one big (but smaller overall) load.

-Blacklists & Annoynce of recipients
Creating X offers instead of 1 can lead to people who decline fast get more than 1 offer,
which will annoy the recipient of the offer, and can cause for unwanted blacklists.

I am open for any questions, including explaining further.