Added a debug toolbar panel for MongoDB
merge with upstream
Dynamic naming added to `DbPanel`
`MongoDbPanel` addition mentioned at CHANGELOG.md and README.md
`DbPanel` summary view fixed
Merge branch 'mongodb-debug-short' of github.com:klimov-paul/yii2 into klimov-paul-mongodb-debug-short
Merge branch 'klimov-paul-mongodb-debug-short'
Adjusted changelog