rpc: add getblockchaininfo and getnetworkinfo

Adds two new info query commands that take over information from
hodge-podge `getinfo`.

Also some new information is added:
- `getblockchaininfo`
  - `chain`: (string) current chain (main, testnet3, regtest)
  - `verificationprogress: (numeric) estimated verification progress
  - `chainwork`
- `getnetworkinfo`
  - `localaddresses`: (array) local addresses, from mapLocalHost (fixes #1734)

src/net.h

@@ -116,6 +116,13 @@ extern CCriticalSection cs_vAddedNodes;
 extern NodeId nLastNodeId;
 extern CCriticalSection cs_nLastNodeId;
 
+struct LocalServiceInfo {
+    int nScore;
+    int nPort;
+};
+
+extern CCriticalSection cs_mapLocalHost;
+extern map<CNetAddr, LocalServiceInfo> mapLocalHost;
 
 class CNodeStats
 {