Add support for specific users/hostnames

[tejacques]

I.E. if your are on the host, host, it would load config.host.json before trying to load config.json.

Similarly, for the process user it would try to load config.user.json before config.json.

Here is the full order:

• config.host.user.dev.json
• config.host.dev.json
• config.user.dev.json
• config.dev.json
• config.host.user.json
• config.host.json
• config.user.json
• config.json