Add support for enabling IAT obfuscation and biased WDist.

Golang's command line parser is slightly cumbersome to use with
subcommands, so the arguments are "obfs4-iatObufscation" and
"obfs-distBias" instead of obfsproxy style subcommands.
Change the drbg seed field in the state file.

Changing from "drbgSeed" to "drbg-seed" to be consistent with the
ServerTransportOptions to allow for easier copy/paste.