Adds a notification system (#4931)

Allows to set up notifications if a specific player connects.

SQL/migrate/V029__player_notifications.sql

@@ -0,0 +1,16 @@
+--
+-- Notifications for Players
+--
+CREATE TABLE `ss13_player_notifications` (
+	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
+	`ckey` VARCHAR(50) NOT NULL COLLATE 'utf8_bin',
+	`type` ENUM('player_greeting','player_greeting_chat','admin','ccia') NOT NULL COLLATE 'utf8_bin',
+	`message` VARCHAR(50) NOT NULL COLLATE 'utf8_bin',
+	`created_by` VARCHAR(50) NOT NULL COLLATE 'utf8_bin',
+	`created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+	`acked_by` VARCHAR(50) NULL DEFAULT NULL COLLATE 'utf8_bin',
+	`acked_at` DATETIME NULL DEFAULT NULL,
+	PRIMARY KEY (`id`)
+)
+COLLATE='utf8_bin'
+ENGINE=InnoDB;