* add -linear-schedule-with-warmup

* update lr scheduler usage in run_glue

* add import info

* add other 5 scheduler with warmup

* add copyright, update usage in run_glue

* simplify argument, make warmup arg support float and int

* Add some LambdaDecay scheduler with warmup, update usage in run_glue

* update classname and unify two cosine decays into one

* update usage in run_glue

* fix typo

* update WarmUp to Warmup, and update class name about Const, and update doc, and usage

* update usage of decay class

* update usage of decay class

* fix doc

* fix version bug

* modify readme

* modify readme

* modify readme

* modify readme

modify ernie_gen README (#5090)

* add ernie_gen

* optimize ernie_gen

* optimize ernie_gen

* optimize ernie_gen code

* fix crf bug

* add ernie_gen __init__.py

* modify nlp version

* fix ernie_gen predict

* optimize doc

* add ernie_gen

* optimize ernie_gen

* optimize ernie_gen

* optimize ernie_gen code

* fix crf bug

* add ernie_gen __init__.py

* modify nlp version

* fix ernie_gen predict

add ernie_gen for the dygraph mode