Made ActiveRecord::isPrimaryKey() public

issue #1207

Eliminating $_GET array

+ added tests and fixed behavior

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