Option type.
'ascii' means using the ascii string that is defined
by hh3cDhcpServer2PoolOptAscii to fill in the option.
'hex' means using the hex string that is defined by
hh3cDhcpServer2PoolOptHexStr to fill in the option.
'ip' means using the IP string that is defined by
hh3cDhcpServer2PoolOptIPStr to fill in the option.