Improve SigHash support

[viter-fb]

Current SigHash enum：

public enum SigHash : uint
{
All = 1,
None = 2,
Single = None | All,
AnyoneCanPay = 128, // 0x00000080
}

Complete SigHash enum：

public enum SigHash : uint
{
ALL(1),
NONE(2),
SINGLE(3),
FORKID(0x40),
ANYONECANPAY(0x80), // Caution: Using this type in isolation is non-standard. Treated similar to ANYONECANPAY_ALL.
ANYONECANPAY_ALL(0x81),
ANYONECANPAY_NONE(0x82),
ANYONECANPAY_SINGLE(0x83)
}