Updating to Netty 4.2

[mohamedhafez]

Just making this request its own issue to for tracking purposes (sorry about the noise in the other issue, I had read 4.2 was backwards compatible so i thought it might be trivial, sounds like its not)

[Lonzak]

+1 to this - the currently used version has several security vulnerabilities and fails for security scanners...

Please see #1117 and also added a merge request with the updates.