Revert "[Network] harmonized Connection message type."

This reverts commit 9dae1c7c5247747ba370dd990120003faceed35e.
We will need USER_INFO to send update of our infos, so we'll need to create
another networkService methods specifically for new Connection broadcast.
[Network] Separated USER_INFO from CONNECTION.

Now both USER_INFO and CONNECTION are possible message type with different
purpose despite having the same content.