Add full type tree and move variable cost options to reference

Author: kdayday

docs/make.jl

@@ -38,13 +38,14 @@ pages = OrderedDict(
             "explanation/per_unit.md",
             "explanation/time_series.md",
             "explanation/example_dynamic_data.md",
-            "explanation/cost_functions.md",
             ],
         "Model Library" => Any[],
         "Reference" =>
             Any["Public API" => "api/public.md",
             "Internal API Reference" => "api/internal.md",
             "Glossary and Acronyms" => "api/glossary.md",
+            "Type Hierarchy" => "api/type_tree.md",
+            "Variable Cost Options" => "api/variable_costs.md",
             "Specifying the category of..." => "api/enumerated_types.md",
             "Developer Guidelines" => "api/developer_guidelines.md",
             "Citation" => "api/citation.md"

docs/src/api/type_tree.md

@@ -0,0 +1,11 @@
+# Type Hierarchy
+
+Here is the complete `PowerSystems.jl` type hierarchy:
+
+```@repl types
+using PowerSystems #hide
+import TypeTree: tt #hide
+docs_dir = joinpath(pkgdir(PowerSystems), "docs", "src", "tutorials", "utils"); #hide
+include(joinpath(docs_dir, "docs_utils.jl")); #hide
+print(join(tt(PowerSystems.IS.InfrastructureSystemsType), "")) #hide
+```

docs/src/explanation/cost_functions.md renamed to docs/src/api/variable_costs.md

@@ -57,9 +57,3 @@ implemented in the package.
 ```@raw html
 <img src="../assets/AbstractTree.png" width="75%"/>
 ``` ⠀
-
-The following code displays the hierarchy, but concrete types are omitted for brevity:
-
-```@repl types
-print(join(tt(PowerSystems.IS.InfrastructureSystemsType, concrete = false), ""))
-```