[shill] Add wpa_supplicant API spec to shill. Also, change 'proxy' -> 'adaptor'

Add the XML description of the wpa_supplicant DBus API, so we can
generate client (proxy object) bindings for it.  to use these
bindings, #include "shill/supplicant_cli.h" and then inherit from the
appropriate class in the fi::w1::wpa_supplicant1 namespace.

For example, for the WPA supplicant "Network" interface:

class SupplicantNetworkProxy : public fi::w1::wpa_supplicant1::Network_proxy {
 public:
  SupplicantNetworkProxy() {}
  virtual ~SupplicantNetworkProxy() {}

  // All signal handlers are abstract in the base class; implement them all here
  virtual void PropertiesChanged(
      const std::map< std::string, ::DBus::Variant >& properties) {
    return;
  }

  // Methods are all implemented for you, as are accessors for properties.
};

BUG=chromium-os:15092
TEST=build

Change-Id: I55e42148bc64965317e7223c852707ed6359b0bc
Reviewed-on: http://gerrit.chromium.org/gerrit/572
Reviewed-by: Chris Masone <cmasone@chromium.org>
Tested-by: Chris Masone <cmasone@chromium.org>
diff --git a/service.h b/service.h
index 3e21acd..b8ca019 100644
--- a/service.h
+++ b/service.h
@@ -54,8 +54,8 @@
   Connection *connection_;
   Device *interface_;
   Endpoint *endpoint_;
-  ServiceProxyInterface *proxy_;
-  friend class ServiceProxyInterface;
+  ServiceAdaptorInterface *adaptor_;
+  friend class ServiceAdaptorInterface;
 };
 
 }  // namespace shill