* rmsprop optimizer support v1 mode

* typo

* optimize code

* refine code

* optimize unit test

* update test_rmsprop_op.py

* update formula of rmsprop

* optimize document

* update API.spec for RMSPropOptimizer

* add default value to check_output_with_place equal_nan

* Fix serious bug in nesterov momentum optimizer.

* remove block api

* remove clone_variable

* hide block inner apis

* update

* fix tests

* refine multi-thread CPU Parallel exe

* refine multi thread CPU Parallel exe

* Refine CPU version for ParallelExecutor

* add share_parameter_between_cards_

* Fix ParallelExecutor bug

* Fix unit test

* Fix parameter opt balance

* Fix with opti (param->grad)

* Add grad to op var

* Remove shard_param_between_cards

* Fix average_accumulate_op for parallel executor.

* Fix model average on multi-GPUs.

* "add float64 tests"

* "fix based comment"

* "fixed based comment"

1. Add attr 'average' into ParamAttr.
2. Make 'params_grads' optional for AverageModel.
3. Add option 'average_mean' and 'average_variance' for batch_normal.

* Add RMSProp optimizer warpper.

* Follow comments.