#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* Cleanup: remove outdated warning for session timeout = 0
- Remove outdated warning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/settings/properties/DatabaseSettings.java

@@ -75,6 +75,10 @@ public final class DatabaseSettings implements SettingsHolder {
     public static final Property<String> MYSQL_COL_ISLOGGED =
         newProperty("DataSource.mySQLColumnLogged", "isLogged");
 
+    @Comment("Column for storing if a player has a valid session or not")
+    public static final Property<String> MYSQL_COL_HASSESSION =
+        newProperty("DataSource.mySQLColumnHasSession", "hasSession");
+
     @Comment("Column for storing players ips")
     public static final Property<String> MYSQL_COL_IP =
         newProperty("DataSource.mySQLColumnIp", "ip");