Keep blank values while parsing POST data.

JSON-RPC and similar protocols send the json data within the key and
leave the value of the "form" empty. So we need to keep form fields with
empty values to be able to access the rpc data.

Signed-off-by: Bernd Zeimetz <bernd@bzed.de>

bottle.py

@@ -693,7 +693,7 @@ def POST(self):
                 fb = TextIOWrapper(self.body, encoding='ISO-8859-1')
             else:
                 fb = self.body
-            data = cgi.FieldStorage(fp=fb, environ=save_env)
+            data = cgi.FieldStorage(fp=fb, environ=save_env, keep_blank_values=True)
             self._POST = MultiDict()
             for item in data.list:
                 self._POST[item.name] = item if item.filename else item.value