Update masternode doc and masternode_list rpc method (#493)

* Update protocol-methods.rst

* Error is raised if the payees is not a list in RPC method masternode_list

docs/protocol-methods.rst

@@ -1069,11 +1069,19 @@ Whenever a masternode comes online or a client is syncing, they will send this m
 
   * *signmnb*
 
-    Signed masternode broadcast message.
+    Signed masternode broadcast message in hexadecimal format.
   
 **Result**
 
   True if the message was broadcasted succesfully otherwise False.
+  
+**Examples**::
+
+  masternode.announce.broadcast("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")
+
+**Example Results**::
+
+  True
 
 masternode.subscribe
 --------------
@@ -1086,6 +1094,8 @@ Returns the status of masternode.
 
   * *collateral*
 
+    The txId and the index of the collateral.
+    
     A masternode collateral is a transaction with a specific amount of coins, it's also known as a masternode identifier.
 
     i.e. for DASH the required amount is 1,000 DASH or for $PAC is 500,000 $PAC.
@@ -1095,6 +1105,10 @@ Returns the status of masternode.
   As this is a subcription, the client will receive a notification when the masternode status changes.
 
   The status depends on the server the masternode is hosted, the internet connection, the offline time and even the collateral amount, so this subscription notice these changes to the user.
+  
+**Example**::
+
+  masternode.subscribe("8c59133e714797650cf69043d05e409bbf45670eed7c4e4a386e52c46f1b5e24-0")
 
 **Example Results**::
 
@@ -1157,4 +1171,4 @@ Returns the list of masternodes.
       ...,
       ...,
       ...
-    ]
+    ]

server/session.py

@@ -543,6 +543,9 @@ class DashElectrumX(ElectrumX):
 
         payees: a list of masternode payee addresses.
         '''
+        if not isinstance(payees, list):
+            raise RPCError(BAD_REQUEST, 'expected a list of payees')
+
         result = []
 
         def get_masternode_payment_queue(mns):