The parameters are encoded on the command line according to the
"application/x-www-form-urlencoded
" convention,
which appends a "?" to the base URL, and then adds name=value pairs
separated by "&" characters, with percent-encoding of
non-URL-friendly characters.
This format is used by many services that require a list of parameters
to be conveyed on the URL.
paramsUrl("http://x.org/", "a", "1", "b", "two", "c", "3&4")
= "http://x.org/?a=1&b=two&c=3%264"