Created by: wangxicoding

PR types

Others

PR changes

APIs

Describe

1. Rename div to divide and refine doc. Deprecated elementwise_div.
2. Add floor_divide. Deprecated elementwise_floordiv
3. Add remainder, and alias mod, floor_mod. Deprecated elementwise_mod

doc PR and preview: https://github.com/PaddlePaddle/FluidDoc/pull/2437 English doc preview: flood_mod and mod is same with remainder.