IOS/ES: Add VerifyContainer

Will be used from several functions to verify the signatures for
different containers (TMDs, tickets, device signed blobs).

An option was added to disable signature checks, because that could be
useful for people trying to import unsigned stuff.

Source/Core/Core/ConfigManager.h

@@ -168,6 +168,8 @@ struct SConfig : NonCopyable
   std::set<std::pair<u16, u16>> m_usb_passthrough_devices;
   bool IsUSBDeviceWhitelisted(std::pair<u16, u16> vid_pid) const;
 
+  bool m_enable_signature_checks = true;
+
   // SYSCONF settings
   int m_sensor_bar_position = 0x01;
   int m_sensor_bar_sensitivity = 0x03;