LP#1777180 Websocketd gateway and test scripts

LP#1777180 Websocketd gateway and test scripts

Adds a new OpenSRF binary/program for relaying websockets messages
to and from a websocketd instance.  The new binary
(osrf-websocket-stdio) performs the same tasks as the
osrf_websocket_translator.c Apache module, minus the Apache module glue
and the extra threading required to run within the Apache module.

Commit includes 2 test scripts (tester.pl and test-stateful.pl) for
generating large series of test messages to send to a websockets
instance. tester.pl sends echo requests only, test-stateful.pl sends
connect->echo-request->disconnect batches across a configurable number
of forked processes.

INSTALL document updated to include websocketd setup as an alternative
to Apache websockets.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Jeff Davis <jeff.davis@bc.libraries.coop>
Signed-off-by: Jason Stephenson <jason@sigio.com>
Signed-off-by: Ben Shum <ben@evergreener.net>