Implement File API

include/AdblockPlus/FileSystem.h

-#ifndef ADBLOCKPLUS_FILE_READER_H
-#define ADBLOCKPLUS_FILE_READER_H
+#ifndef ADBLOCKPLUS_FILE_SYSTEM_H
+#define ADBLOCKPLUS_FILE_SYSTEM_H
 
 #include <istream>
 #include <string>
 #include <memory>
 
 namespace AdblockPlus
 {
-  class FileReader
+  class FileSystem
   {
   public:
-    virtual ~FileReader();
+    struct StatResult
+    {
+      bool exists;
+      bool isDirectory;
+      bool isFile;
+      int64_t lastModified;
+    };
+
+    virtual ~FileSystem() {}
     virtual std::auto_ptr<std::istream> Read(const std::string& path) const = 0;
+    virtual void Write(const std::string& path, const std::string& content) = 0;
+    virtual void Move(const std::string& fromPath,
+                      const std::string& toPath) = 0;
+    virtual void Remove(const std::string& path) = 0;
+    virtual StatResult Stat(const std::string& path) const = 0;
   };
 }
 
 #endif