try using the new Docker setup of travis-ci

- do not allow boolean values for integer columns
- use native boolean type with boolean values
- removed workaround that turned out to be wrong when schema and values
  are used correctly. Workaround resulted from wrong usage of boolean
  values before.

fixes #4672

[ci skip] unneeded use Model

speed up process a lot because 3 composer updates are reduced to one

Revert "Fixes #4829: Removed `PARSING_ONLY` from `\yii\rest\UrlRule` to allow creating non-GET URLs for forms and tests"

This reverts commit 4ffbfec9.

Fixes typo in concept-configurations.md

Fixes #4829: Removed `PARSING_ONLY` from `\yii\rest\UrlRule` to allow creating non-GET URLs for forms and tests

Fixes #4188: API exceptions are now exposing less data when YII_DEBUG is false

- If exception is internal it's always returned as HTTP 500 general purpose one.
- Type isn't exposed anymore.

[ci skip] Fixes typo in structure-assets.md