Add region actor

- [x] Define a `ID`
- [x] Store the player and energy in a `Set`.
- [x] Create the initial state with unique ID for each entities
- [x] calculate the AOI of a player
- [x] Initiate a new game stage
- [x] Notify the last world state at the journal
- [ ] store the event in a DB (file) : create, destroy, move (optional)
- [x] Check if the player move from a region to another one. If it is then you send a `transfer` message to the proxy (That need some requirement of #19: moved player message)