Add a `DEFAULT_CONFIG_PATH` and ConfigSettings::readSetting(char*) scaffold

This will serve as the API to populate the settings from
a file on disk before evaulating command line arguments.
A simple key=value config parser

With comments
Whitespace.
_trim_string() is now TRIM_STRING() the macro
Centralize settings concerns in settings.cpp/h
Fail a config read if we can't read it instead of setting 0 settings
Add -c <config> option to read a non-default config
Actually fail the read if a key is unknown
Merge pull request #55 from sshirokov/config-file

Support for loading Configuration Files