Sharding, connection improvements

[nayvcake]

Sharding should be improved in the connection part and the reconnection method. Some options should be removed to let the library handle it automatically. Below is the roadmap for the current sharding implementation.

• Improve reconnection
• Implement a RetryConnection system
• Enhance cache system
• Improve connection closing
• Implement/Improve error handling
• Improve event system
• Improve the session resumption method