This builds on the new dbus role support to provide a minimal example proxy
between ws and dbus.
A client app is provided that asks the proxy to connect to libwebsockets.org
and proxy the drawing data from the mirror example there back to the dbus
client using dbus messages.
Several new ops are planned for tls... so better to bite the bullet and
clean it out to the same level as roles + event-libs first.
Also adds a new travis target "mbedtls" and all the tests except
autobahn against mbedtls build.
