Feature migrations up/down (#270)

* Migrations up down

* Add forum model

* Syntactic sugar for db structure changes

* Refactor migrations with $up & $down

* Fix migrations upgrade and downgrade

+ Add option to disable auto migrate

* Add migrate:to command

Usage: php aac migrate:to x (x - database version)

* Show error when mail is not enabled

* Fixes regarding to init.php

* Add migrate command to manually upgrade db, incase auto migrate is disabled

* Fixed rest of the migrations

* Limit max version of database

* Don't allow minus number

* Option to clear specified plugin settings by name

* Version is required

* Fix PHPStan errors

* Unset $up after migration, to prevent executing same migration twice

* Add database version to output

* This is not needed

* Update 5.php

* Set database_auto_migrate on install

* Set blank & color only if current db version supports it

* Fix duplicate function declaration

system/migrations/24-items.sql

@@ -0,0 +1,9 @@
+CREATE TABLE `myaac_items`
+(
+	`id` INT(11) NOT NULL,
+	`article` VARCHAR(5) NOT NULL DEFAULT '',
+	`name` VARCHAR(50) NOT NULL DEFAULT '',
+	`plural` VARCHAR(50) NOT NULL DEFAULT '',
+	`attributes` VARCHAR(500) NOT NULL DEFAULT '',
+	PRIMARY KEY (`id`)
+) ENGINE=InnoDB DEFAULT CHARACTER SET=utf8;