Most of XamContent* methods, besides enumeration.

Progress on #152.

src/xenia/kernel/fs/entry.cc

@@ -29,6 +29,10 @@ Entry::Entry(Device* device, const std::string& path)
 
 Entry::~Entry() = default;
 
+bool Entry::is_read_only() const {
+  return device_->is_read_only();
+}
+
 }  // namespace fs
 }  // namespace kernel
 }  // namespace xe