base/json: Add a simple Read() which reads in a whole json file.
base/json: Eliminate some unnecessary copies (Force move of everything instead)
base/json: Include what was found as well as what is expected.
base/json: Match exactly what is asked for

Before we greedily matched anything which was not whitespace. So we'd read in commas after exact matches, for instance "true,".
base/json: Better error message
Switch <base/cmd> to use <base/json> rather than <starsha/note> for args file parsing