Create ColumnSchema.php
Create QueryBuilder.php
Create Schema.php
Edited introduction.
Edited the first quarter
updated doc.
Coding style PSR-2
tag for MongoDB unit tests fixed
Translating SQL-like syntax into Mongo syntax removed from "\yii\mongodb\Collection".
Replace request with response in code example
Merge pull request #1465 from Bethrezen/patch-3

Replace request with response in code example
added support for updateCounters to elasticsearch

issue #1313
Merge pull request #1406 from p0larbeer/master

DB Schema OCI
clean up oci driver.
moved twig to yii subdirectory.
moved smarty to yii.
moved extensions under yii.
fixed test breaks.
fixed composer.json for yii-dev.
Fixes #1472: set event sender if possible.