Added byte[] into ExperimenterAction

Signed-off-by: Michal Polkorab <michal.polkorab@pantheon.sk>
ExperimenterAction length computation added

Signed-off-by: Michal Polkorab <michal.polkorab@pantheon.sk>
Bumped Netty to 4.0.17.Final (to match controller's version)

Signed-off-by: Michal Polkorab <michal.polkorab@pantheon.sk>