[rpc] Add logging RPC

Adds an RPC to get and set currently active logging categories.

src/rpc/client.cpp

@@ -113,6 +113,8 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "getmempoolancestors", 1, "verbose" },
     { "getmempooldescendants", 1, "verbose" },
     { "bumpfee", 1, "options" },
+    { "logging", 0, "include" },
+    { "logging", 1, "exclude" },
     // Echo with conversion (For testing only)
     { "echojson", 0, "arg0" },
     { "echojson", 1, "arg1" },