[PPML] update simple query example

[PatrickkZ]

Description

update the simple query example with PPMLContext in both python and scala api. add more usage example and dataframe operation example.

1. Why the change?

the old simple query example is too simple, so add more usage example of PPMLContext in both python and scala api.

2. User API changes

N/A

3. Summary of the change

add more usage example of PPMLContext in both python and scala api.

4. How to test?

• [ ] N/A
• [x] Unit test
• [ ] Application test
• [ ] Document test
• [ ] ...