fixes #422

fixed some issues with schema detection

fixes #3233

- Removed `form_begin`, `form_end`
- Added `use()` and `ViewRenderer::uses` that are importing classes and namespaces
- Added widget dynamic functions `*_begin`, `*_end`, `*_widget`, `widget_end`
- Added more tests

issue #3520

breaking changes.

Fixes #2955: Changed the signature of ActiveQuery constructors and `ActiveRecord::createQuery()` to simplify customizing ActiveQuery classes

Fixes #2726: ActiveRecord now fills default values on creating new instance of the model if defaults are available from DB schema