Original Classes of Entity Wrapper are Threw Away

[Echo-az]

Describe the bug
The classes of entity wrapper are set to generateEntityClassNames. As a result, the original classes are threw away.

To Reproduce
Steps to reproduce the behavior:

1. Create an entity with customized classes
2. Trigger model to dom

Expected behavior
Original classed are kept

Device Information

• OS: macOS
• Browser: WebKit/Safari
• Version: latest

Additional context
I know we can workaround this problem by adding a child container div with classes we want. But I think throwing away original classes may not be reasonable.

[Echo-az]

Tried #2752 to fix this problem