feat(env): add manager for db operation and add dot env.example

.gitignore

 .idea/
 .ycm_extra_conf.py
 __pycache__
+
+.env

pyengine/engine/.env.example

+DEBUG=True
+SQLALCHEMY_TRACK_MODIFICATIONS=False
+SECRET_KEY=test
+SQLALCHEMY_DATABASE_URI=mysql+pymysql://vecwise@127.0.0.1:3306/vecdata
+
+ROW_LIMIT=10000000
+DATABASE_DIRECTORY=/tmp

pyengine/manager.py

+from flask_script import Manager
+
+from engine import db, app
+
+manager = Manager(app)
+
+@manager.command
+def create_all():
+    db.create_all()
+
+@manager.command
+def drop_all():
+    db.drop_all()
+
+@manager.command
+def recreate_all():
+    db.drop_all()
+    db.create_all()
+
+if __name__ == '__main__':
+    manager.run()