Instructions for compiling on Ubuntu 17.04 Zesty

https://sexcoinforum.com/index.php?topic=171.0

Basically, the same instructions as 16.04 except we have to install and use gcc5 as 17.04 comes with gcc6. I'm hoping the issue with gcc6 is an easy fix that can be deployed with a future release, but no guarantees as I don't know C/C++.

I've also added two dependencies to the original dependency list for people who want to build nodes in docker. The officially maintained docker images for Ubuntu are missing a few things that would be on any normal minimal install of Ubuntu.