Option to set environment variables through settings.json

[GoogleCodeExporter]

It works on my machine because I have python installed. One of users reported a 
problem that it's not working on his computer, see:

https://groups.google.com/d/msg/phpdesktop/8vgK2pmmszs/YSRHj5Hzl6oJ

Original issue reported on code.google.com by czarek.t...@gmail.com on 28 Apr 2014 at 1:12