debugger WIP
Merge pull request #2 from yiisoft/master

Merge from yiisoft/master
Invert the condition in AssetConverter
Merge pull request #607 from DsXack/master

Fix the condition in AssetConverter
initial implementation of Yii debugger.
Merge branch 'master' of github.com:yiisoft/yii2
minor issue fixes.
Debugger: database panel WIP
debugger furnishing
Removed test code.
debugger minmax wip
Implemented minimize and maximize of debugger toolbar.
finished debugger.
minor fixes.
Minor fixes.
normalize header names.
Added DataProvider and IDataProvider.
Merge branch 'master' of github.com:yiisoft/yii2
Added support for using callables as "ActiveQuery::indexBy".
Virtual properties documentation has been added to "web\Session"