Gridopt

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* Added slack P participation to non-nr acpf for consistency.
* Updated to modular heuristic.
* Made unittests handling of test cases and solution files cross-platform.
* Made test utils more flexible to be used from outside unittests.
* Added HVDC, FACTS and vdep-loads to ACPF.
* Added option for using linearized AC power flow equations in ACPF.
* Specified gridopt command-line utility using console entry point.
* Added command-line utility option for writing network to file.

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* Changed ACPF based on NR to use new PVPQ switching constraint from PFNET.
* Added pvpq_start_k parameter to ACPF to control start iteration of PVPQ switching heuristics.
* Updated ACPF method class to work as a parent method class.
* Made thermal_limits param for ACOPF take on values 'none', 'nonlinear', and 'linear' (lineflow).

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* Reduced width of ACOPF output per iteration.
* Updated ACOPF regularization param names to be more consistent with those of ACPF.
* Hid internal param data structure from user in power flow methods, and allowed saving/restoring params including optsolver parameters.
* Changed method results and mechanism for storing solution and updating network.
* Moved location of command-line unitlity.
* Fixed bug in NR ACPF related to tap_changers vs tap_changers_v.
* Changed travis to get pfnet and optalg from pypi.
* Added "solver name" to method results.
* Changed "optsolver" to "solver" and added "solver" to DCPF.

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* Unified methods (ACPF, ACOPF, DCPF, DCOPF) with param "optsolver" for choosing optimization solver.
* Added documentation for "gridopt" command-line utility.
* Updated and re-enabled DCOPF unittests.
* Added new OPTALG solver "inlp" to ACPF and ACOPF and updated documentation.
* limit_gens flag for non-NR ACPF with unittest.

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* Compatibility with PFNET v1.3.0.
* Compatibility with OPTALG v1.1.3.
* Thermal limits option for AugL and Ipopt OPFs.

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* Compatibility with PFNET 1.2.9.
* Tool for transforming PFNET to OPTALG problems and recovering primal and dual variables.
* Standard OPF problem formulation.
* OPF method based on AugL uses linear variable bounds and handles them with barrier.
* OPF method based on IPOPT solver.
* Flat start option in gridopt script.
* Travis continuous integration.
* Readthedocs.