Configuration-free server

[godbyk]

Since the default config file for osvr_server is now empty, why should osvr_server require a configuration file be present at all? I propose the following behavior:

1. If a configuration file is provided on the command line, use it (if it exists).
2. Failing (1), if an osvr_server_config.json file is available in the current working directory use it.
3. Failing (1) and (2), start the server using an empty { } configuration.

[d235j]

I'd like to extend this a bit: between 1 and 2, look in a system path (such as $PREFIX/share).
#238 should probably be resolved first.

[rpavlik]

Yes, it should presumably have a search path including a user directory, etc. (The osvr_server binary itself is incredibly minimal - doesn't even have a proper command-line-parsing framework in use - has been basically a "good enough" launcher for the functionality that's added primarily in the osvrServer library, with little engineering attention paid to it.)

[Outurnate]

I'll take this one on