Docplex

* In ``docplex.mp``:
* Latest supported CPLEX Optimization Studio is now 20.1

* In ``docplex.mp``:
* Fixed a bug with pickling: edition of a constraint in a pickled model raised an error
* Fixed a bug with pickling: models with piecewise-linear constraints could not be pickled

* In ``docplex.cp``:
* Add environment variable DOCPLEX_CP_CONTEXT to modify configuration
* Add new module check_list that print a report on execution environment
* Remove DOcloud from documentation (including code)
* Rework customization of configuration and better support of default directory
* Add new configuration parameter model.sort_names to drive sort of variable declarations in CPO file format.
* Fix a problem that may crash Python in case of abort_search with local solve.

* In ``docplex.mp``:
* add `Model.add_quadratic_constraints()` to add a batch of quadratic constraints
* add `Model.populate_solution_pool()` for a native support of solurtion pools
* support of CPLEX 20.1
* compatible with Python 3.8 (only with CPLEX 20.1)
* enable changing absolute and relative tolerances for multi-objectives
* Optimization of `Model.if_then`: when condition is of the form `b==1` (or 0), no additional boolean
variable is generated
* For solving, `docplex.mp` now uses the `cplex` module if it has been installed. If not, `docplex.mp`
checks for the latest installed version of CPLEX Optimization Studio (COS) (using the CPLEX_STUDIO_DIRXXX
environment variables) and use the `cplex` if a COS is found, unless the configuration of the engine
states otherwise.

* In ``docplex.cp``:
* Add pngfile= parameter to visu.show() method to store in a PNG file instead of display on screen.
* Make parameters and solver infos also available in refine_conflict solution.
* Add a IntegerDomain class used to represent domain of integer variables, with a specific __str__ method
* Add new functions ceil(), floor(), trunc(), round() and sgn()
* Remove all warnings generated by Python 38
* Optimize creation of add expressions with CumulExpr and zero
* Implement configurable factorization of common model expressions when generating CPO format
* Add checking of scal_prod() array sizes at modeling time
* Add strict_lexicographic() and checking of strict_lexicographic() and lexicographic() array sizes at modeling time.
* Add failure explanation as new method explain_failure() allowing to log failure tags or get details on one or several failures.
* Enhance management of local solve sub-process timeout with detailed error and configurable timeout delay
* For solving, `docplex.cp` now uses the `cpoptimizer` executable if it has been installed. If not, `docplex.cp`
checks for the latest installed version of CPLEX Optimization Studio (COS) (using the CPLEX_STUDIO_DIRXXX
environment variables) and use the `cpoptimizer` if a COS is found, unless the configuration of the engine
states otherwise.
* Support last optimal solution in search/next sequence
* Support of solver parameters in all next() solutions
* Add solver version in process info attached to a run result

* In ``docplex.mp``:
* add Model.quadratic_dual_slacks()
* Fixed a bug in multi-objectives: objectives were incorrectly rounded
* Fixed a bug in Model.report(): multiple objective values were not displayed()
* In ``docplex.cp``:
* Add conflict in CPO format in refine conflict result
* Fix problem when parsing KPIs section of a CPO model
* Add method add_constraint() to model for compatibility with docplex.mp
* Comment method get_fail_status() of SolveResult as deprecated.
* Fix problem of wrong import of deque in collections.abc

* Updated tracking events in Watson studio notebooks.
* In ``docplex.mp``:
* Model.solve() will not use solve on cloud unless `agent` is specifically set to 'docloud`.

* Removed dependency to the `docloud` package. Now you need to explicitely install the package using `pip install docloud` to use DOcplexcloud.
* In ``docplex.mp``:
* added Model.export_as_mps_string(), Model.export_as_sav_string()
* fixed a bug with dettime_limit: solving with a deterministic time limit
was mis-interpreted as a solve failure, returning None.
* fixed bug on cplexcloud solve: number of nodes processed was always zero.
* repeated solves incorrectly restarted from start of search, now start from where the last solve stopped.
* added keyword argument 'time_limit' to Model.solve() to set a temporary time limit.
* added new method SolveSolution.is_valid_solution()
* fixed a bug in ModelReader: ranged constraints bounds were inverted when reading from SAV or MPS.
* fixed a bug in Model.set_lex_multiobj(): arguments abstols, reltols were ignored.
* added proper type-checking for Model.add_indicator_constraints()
* added docplex.mp.check_list/py to check local installation.
* In ``docplex.cp``:
* Enable reading of line directives when parsing a CPO file
* Remove parameter LogSearchTags from public parameters
* Fix a minor problem concerning compilation of KPI expressions in CPO format