helpers.cpp: Add new functions

- readFile()
  - parseJsonFromFile()
  - parseJsonFromString()

  parseJsonFromString() and parseJsonFromFile() use Json::CharReader
  instead of the obsolete function Json::Reader

src/system/helpers-json.h

@@ -0,0 +1,31 @@
+#ifndef __system_helpers_json__
+#define __system_helpers_json__
+
+/*
+	Neutrino-HD
+
+	License: GPL
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program; if not, write to the Free Software
+	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <json/json.h>
+
+using namespace std;
+
+bool parseJsonFromFile(string& jFile, Json::Value *root, string *errMsg);
+bool parseJsonFromString(string& jData, Json::Value *root, string *errMsg);
+
+#endif