Miscellaneous improvements

[WumboSpasm]

• Added previously-missing flags for settings defined in proxySettings.json, and vice versa
• Reordered and renamed some settings to be more consistent/predictable
• proxySettings.json is now always loaded from the same directory as the executable, rather than the working directory
• Fixed redundancy in startup command-line output
• Replaced deprecated ioutil package with io
• Added missing error check for proxy responses