Feature Request: let splitpath also handle the query intelligently

[schlichtanders]

Currently splitpath already extracts path parts from the path string, but
leaves the query string as is, which is too raw for most/all demands which work with the query.

The URIs package already provides the respective extractor function queryparams(::URI). Hence the suggestion to extract this directly in the default function

function splitquery(app, req)
  uri = req[:uri]
  req[:path] = splitpath(uri.path)
  req[:query] = queryparams(uri.query)  # new
  app(req)
end

Edit: if changing the function is too tough because of backwards compatibility, we could name the function splituri instead.