Add ravens output (#6)

* WIP: math2ravens solution converter. Added Voltages, Statuses, and PowerFlows basic structures.

* WIP: Add support for adding status to transformers coming from MATH model.

* WIP: add operational results switch states and return values for transformation.

* WIP: Add mn support for voltages.

* ADD: multinetwork support for PF/OPF solutions.

* ADD: support for ONM solutions states, status.

* ADD: support for storage power flows and correct timestep values to hours based on time elapsed.

* FIX: check for existence of state and status keys.

* REF: sort the nws in mn solutions, making sure the timesteps are ordered.

Author: juanjospina

src/PowerModelsDistribution.jl

@@ -70,6 +70,7 @@ module PowerModelsDistribution
     include("data_model/transformations/dss2eng.jl")
     include("data_model/transformations/eng2math.jl")
     include("data_model/transformations/math2eng.jl")
+    include("data_model/transformations/math2ravens.jl")
     include("data_model/transformations/utils.jl")
     include("data_model/transformations/reduce.jl")
     include("data_model/transformations/ravens2math.jl")