[Capped Futures] Market settlement

[jeremyletang]

When binary_settlement parameter is set to false any value 0 <= settlement_price <= max_price should be accepted as a settlement price.

When binary_settlement parameter is set to true only settlement_price=0 or settlement_price=max_price should be accepted.

Any other values get ignored and market does not settle, instead it still waits for subsequent values from the settlement oracle until a value which passes the above conditions arrives.