Db traits

Fixed gii after merge #1184

[ci skip]

strict sql dbms like postgres would fail otherwise

this allows us to implement other activerecord implementations based on
NoSQL dbms

Move AppAsset from config to assets directory

Updated AR classes with the latest changes from master to go on with
separation of AR query classes in traits.

Conflicts:
	framework/yii/db/ActiveQuery.php
	framework/yii/db/ActiveRecord.php
	framework/yii/db/ActiveRelation.php

Using only arrays in rules instead comma-separated string

also removed superflous minimum-stability definition

- added example code for application components
- added missing short description

[ci skip]

Little helpful description for Session::cookieParam

allows opening email for view in mail program directly

Code style