#1031 Introduce hasSession field in datasource (#1351)

* Introduce hasSession field in datasource

That makes isLogged more consistent as it will be '1' only when the player is online.

* Fixes

* Fix unit testing

* Update config doc

* Create SessionService

* Create test for SessionService, avoid DB operations if sessions are disabled

* Cleanup: remove outdated warning for session timeout = 0
- Remove outdated warning
- Encapsulate session enabled check in SessionService

* Fix failing SessionServiceTest, add data source integration tests for session methods

src/main/java/fr/xephi/authme/process/quit/AsynchronousQuit.java

@@ -82,8 +82,11 @@ public class AsynchronousQuit implements AsynchronousProcess {
         playerCache.removePlayer(name);
 
         //always update the database when the player quit the game (if sessions are disabled)
-        if(!wasLoggedIn || !service.getProperty(PluginSettings.SESSIONS_ENABLED)) {
+        if (wasLoggedIn) {
             database.setUnlogged(name);
+            if (!service.getProperty(PluginSettings.SESSIONS_ENABLED)) {
+                database.revokeSession(name);
+            }
         }
 
         if (plugin.isEnabled()) {