* initial commit

* fix error

* fix typo and order

* "polish code"

* "fix ci"

* "fix ci"

* "done"

In this way we can build and test using WITH_FLUID_ONLY flag being set
to ON.

- move paddle.v2.dataset,reader to paddle.dataset,reader
- remove unused code (which depends on v2) in paddle.dataset,reader

Fix dist error with lr decay layer

This reverts commit ce16400d.

* "add functors"

* "remove old code"

* "fix"

* "fix ci"

* "add details"

* "fix ci"

* "fix ci"

* "fix ci"

* "fix ci"

* "remove unused code"