Fixes #2360: Added `AttributeBehavior` and `BlameableBehavior`, and renamed `AutoTimestamp` to `TimestampBehavior`

Fixes #2490: `yii\db\Query::count()` and other query scalar methods now properly handle queries with GROUP BY clause

- supports GFM now
- allows defining different flavors

fixes #47

Fixes #1881: Improved `yii\bootstrap\NavBar` with `containerOptions`, `innerContainerOptions` and `renderInnerContainer`

Fixes #1186: Changed `Sort` to use comma to separate multiple sort fields and use negative sign to indicate descending sort

#2436 override the function `getAttributeLabel` in `BaseActiveRecord` to receive label of the attribute, which looks like `relatedMode.attribute`, from the related model

#2436 override the function `getAttributeLabel` in `BaseActiveRecord` to receive label of the attribute, which looks like `relatedMode.attribute`, from the related model

#2436 override the function `getAttributeLabel` in `BaseActiveRecord` to receive label of the attribute, which looks like `relatedMode.attribute`, from the related model

Why use a strong random number generator in one place, but not another? I know salts have no cryptographic security requirement, but collisions are less likely if you use one.

Removed unnecessary PHPDoc property (https://github.com/yiisoft/yii2/commit/ce04134db24d3bcdc0388f5b7832dd1dbb1945ef)

fixes #2370