Add some comments
Send force-login message with 15 tick delay
Add missing braces
Add javadoc to and refactor isPlayerForcedToLogin()
Store username in a local variable
Refactor free-slots checking
Refactor ServerEventListener
Rename local "preserveSlotsPlayers" to "preserveForPlayers"
Add PlayerHolder

This commit adds a PlayerHolder singleton class, which is a storage for
both online and offline players, and puts a registerListenerForPlugin()
call in LogItPlugin.
Do nothing if a session has already been created
Refactor destroySession()
Remove isSessionAlive(String) and refactor isSessionAlive(Player)
Add MinecraftUtils
Remove InventoryDepository.saveInventory()
Do nothing if a session has already been started
Do nothing if a session has not been started
Return instead of throwing AccountNotFoundException

This commit replaces "throw new AccountNotFoundException()" statements
in getAccountPersistence() and updateAccountPersistence() with "return".
Add IoUtils
Use our IoUtils instead of Apache IOUtils
Organize imports