Support multiple warnings in RPC responses

Following #353.

json/src/lib.rs

@@ -118,7 +118,7 @@ pub struct GetNetworkInfoResult {
     pub incremental_fee: Amount,
     #[serde(rename = "localaddresses")]
     pub local_addresses: Vec<GetNetworkInfoResultAddress>,
-    pub warnings: String,
+    pub warnings: StringOrStringArray,
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Deserialize, Serialize)]
@@ -517,7 +517,7 @@ pub struct GetMiningInfoResult {
     pub pooled_tx: usize,
     #[serde(deserialize_with = "deserialize_bip70_network")]
     pub chain: Network,
-    pub warnings: String,
+    pub warnings: StringOrStringArray,
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Deserialize, Serialize)]
@@ -1005,7 +1005,7 @@ pub struct GetAddressInfoResult {
 }
 
 /// Used to represent values that can either be a string or a string array.
-#[derive(Clone, Debug, Deserialize, Serialize)]
+#[derive(Clone, Debug, Deserialize, PartialEq, Eq, Serialize)]
 #[serde(untagged)]
 pub enum StringOrStringArray {
 	String(String),