* add static_only for static api

* addd static_only for class init

* remove static_only for default_main_program

* remove creater_parameter & startup_program

* remove failed apis

* revert py_func import

* remove global scope

* remove some api

* remove cuda pinned place

As the title

This PR enhances error messages of several API/OPs:

ParallelExecutor (python && C++)
Executor (python && C++)
StaticRNN (python)
IfElse (python)
cond (python)
split_lod_tensor (python && C++)

* fix fluid.data
test=document_fix

* fix doc batch dim
test=document_fix

* polish executor doc
test=develop

* remove compile from PE
test=develop

* update exe.run

* fix code bug
test=develop

test=develop

* reset drop local scope counter
test=develop

* polish doc
test=develop

* updata parallel executor doc
test=develop

* update API.spec
test=develop

* polish code
test=develop

test=develop

test=develop

* unified PE and compiler
test=develop

* Polish code
test=develop

* unified PE and compiler
test=develop

* Polish code
test=develop

* Unified ParallelExecutor and Compiler

test=develop

* Unified ParallelExecutor and Compiler

test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

* Refactor ParallelExecutor
test=develop

* extract Reduce and AllReduce mode from MultiDevSSAGraphBuilder
test=develop

* Refactor MultiDevSSAGraphBuilder
test=developt

* Remove enable_data_balance
test=develop

* code refine
test=develop

* remove data balance
test=develop

* refine ScaleLossGradOp
test=develop

* remove uncessary file
test=develop

* code refine
test=develop

* modify  function name
test=develop

* follow comments
test=develop

* add is_distribution field
test=develop

* set is_distribution
test=develop

* fix DistSSAGraphBuilder
test=develop

test=develop