chan_websocket: Allow additional URI parameters to be added to the outgoing URI.

chan_websocket: Allow additional URI parameters to be added to the outgoing URI.

* Added a new option to the WebSocket dial string to capture the additional
  URI parameters.
* Added a new API ast_uri_verify_encoded() that verifies that a string
  either doesn't need URI encoding or that it has already been encoded.
* Added a new API ast_websocket_client_add_uri_params() to add the params
  to the client websocket session.
* Added XML documentation that will show up with `core show application Dial`
  that shows how to use it.

Resolves: #1352

UserNote: A new WebSocket channel driver option `v` has been added to the
Dial application that allows you to specify additional URI parameters on
outgoing connections. Run `core show application Dial` from the Asterisk CLI
to see how to use it.