Add Nanostack configurations

Author: Seppo Takalo

tools/config.py

@@ -347,8 +347,10 @@ class Config(object):
 
     # Allowed features in configurations
     __allowed_features = [
-        "UVISOR", "BLE", "CLIENT", "IPV4", "IPV6", "COMMON_PAL", "STORAGE"
-    ]
+        "UVISOR", "BLE", "CLIENT", "IPV4", "COMMON_PAL", "STORAGE", "NANOSTACK",
+        # Nanostack configurations
+        "LOWPAN_BORDER_ROUTER", "LOWPAN_HOST", "LOWPAN_ROUTER", "NANOSTACK_FULL", "THREAD_BORDER_ROUTER", "THREAD_END_DEVICE", "THREAD_ROUTER"
+        ]
 
     def __init__(self, tgt, top_level_dirs=None, app_config=None):
         """Construct a mbed configuration