* Fix old documentation for channel_recv
* Initial design of CSP select
* Redesign channel implementation for Select Op
* Remove unecessary header
* Initial checkin of select op, currently will read all the conditional_op in the cases block and also pull out all channels involved in the select.
* Init python select op API
* Python select bug fix when checking op creates block
* Add case_to_execute as (a) input to select, (b) into the passed inputs into the select op
* Add in addition code for select op
* Init fibonacci test from python
* implement fibonnaci sequence test
* update fib unit test
* Improve select test cases
* Shorten non-pep-8-ed lines
* Add methods on channel needed by select op
* Fix compile issues, finish implementation, still need to debug code
* Fix issue with fibonncci test, it works now!
* Change QueueMessage callback to take in an ChannelAction enum, fix select unit test
* Fix case attributes
* Fix issue with select control flow
* Make cases - previously on each selectcase conditional_block - attributes to select
* Use class constants for type of channel
* Change select op to take in "cases" attribute
* return boolean from select callback function to tell Channel if this RECV or SEND should be executed
* Improve attributes and inputs comments on select op
* Fix issues with python unit test
* Assert fibonacci final output
* Fix issue when channel name / channel var is null for "default" case in select op
* Assert base select test output
* Make QueueMessage use shared pointer and modify the order of the callback
* Fixing the order in which the callback is called
* Move channel utility methods to paddle/fluid/operators/concurrency/channel_util
* Create channel_util and move channel util methods
* Fix crash when calling select_op
* Fix deadlock
* Fix issue of channel destructor deadlock
* Fix precommit issues
* Accidentally checked in changes to beam_search_op, reverting change.
* Fix dependency issue in concurrency cmake
* add device_context dependency for concurrency target
Abhinav Arora
Thuan Nguyen