Created by: chenwhql

fix some problems in StaticModelRunner:

1. save model no extra scale

Now in paddle, the model saved by save_inference_model will add extra scale layer before fetch, but this feture is added before a year, the model was trained before one year may not hold this scale layer, this PR adapt this case.

2. inference result error

inferencing use changed program desc by StaticModelRunner, only change is_test is not equal to using original program desc, so changing using original loaded program desc.

3. multiple inputs order error

reverse input variables order

4. change forward inputs to *args

support multiple inputs instead of list[var]

5. polish doc