Hobbit-core

* Enhance gen cmd: now can auto create CRUD API and tests.

* Add template for 4-layers (view、schema、service、model).
* Add options api for query all consts defined in `app/models/consts`.
* Removed example code.
* Split hobbit cmd and hobbit_core lib, now install cmd should be `pip install "hobbit-core[hobbit,hobbit_core]"`.
* Remove flask_hobbit when import (`hobbit_core.flask_hobbit.db import transaction` --> `from hobbit_core.db import transaction`).

* The strict parameter is removed in marshmallow >= 3.0.0.

* Add import_subs util for auto import models、schemas、views in module/__init__.py file.
* Add index for created_at、updated_at cloumn and default order_by id.
* Add validate for PageParams.
* Add hobbit gen cmd for auto render views.py, models.py, schemas.py etc when start a feature dev.
* Add ErrHandler.handler_assertion_error.
* Add db.transaction decorator, worked either autocommit True or False.
* pagination return dict instead of class, order_by can set None for
* traceback.print_exc() --> logging.error.
* Foreign key fields support ondelete, onupdate.
* Hobbit startproject cmd support celery option.

* Add index for created_at、updated_at cloumn.

* traceback.print_exc() --> logging.error.