Merge Windows Driver Code (#817)

This is the first of the Windows implementation code that will be merged. This is only the driver code.

Also note the updates to the appveyor configuration. It now builds, installs and queries the status of driver directly on the build machine. Then it builds an 'artifact' which is essentially the binaries packaged up.

include/openthread-types.h

@@ -45,7 +45,7 @@ extern "C" {
 #endif
 
 #ifdef _WIN32
-#ifdef WINDOWS_KERNEL
+#ifdef _KERNEL_MODE
 #include <ntdef.h>
 #else
 #include <windows.h>

include/platform/settings.h

@@ -35,8 +35,7 @@
 #ifndef OT_PLATFORM_SETTINGS_H
 #define OT_PLATFORM_SETTINGS_H 1
 
-#include <stdint.h>
-#include <openthread-instance.h>
+#include <openthread-types.h>
 
 #ifdef __cplusplus
 extern "C" {