Impl scalar switch case op with condition op

* Update csp.md

* Update csp.md

* Update csp.md

* Add proposed fluid syntax for select statement in Fluid's implementation of CSP

* Fix Typo

* Adding send and recv in design doc

* fix typo

* fixed code

* Adding threading

add switch op design

* fix typo

* fix typo

* fix some typos

* fix

Add `ProgramDesc` storage

* Add csp.md

* update csp.md

neural machine translation model support beam search with while op

* Add fluid_compiler.md

* Paragraphing

* update switch_kernel.md

* update the demo code

* update

Make users can access parameters of layers and their gradients.

* "remove cudnndevicecontext"

* "remove unused init code"

* "fix hash functions"