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 pull request #1 from yiisoft/master

switching base
new translation
new translation
update Chinese guide.
update Chinese guide.
update start-installation.md Chinese version.
proofread start-hello.md Chinese version.
proofread start-forms.md Chinese version.
proofread start-databases.md Chinese version.
sync images to Chinese version guide.
update start-gii.md Chinese version.
update start-looking-ahead.md Chinese version.
update structure-overview.md Chinese version.
proofread structure-entry-scripts.md Chinese.
copy files, prepare to translate.