Restructure API Reference content to improve left sidebar (#1598)

* split pv_modeling.rst into a directory

The left sidebar in pydata-sphinx-theme reflects document hierarchy, without considering in-page headers.  To get those headers into the sidebar, we have to rework the document hierarchy such that the former in-page headers are now reflected in the document structure.  Not ideal, but it's the only way I've found so far.

* split up effects_on_output and irradiance; use top-level toctree folder

* add dropped entries from merge

* put back ADR entries

* put back astm_e1036

Author: kandersolar

.gitignore

@@ -40,6 +40,7 @@ pvlib/spa_c_files/spa_tester.c
 
 # generated documentation
 docs/sphinx/source/reference/generated
+docs/sphinx/source/reference/*/generated
 docs/sphinx/source/savefig
 docs/sphinx/source/gallery
 

docs/sphinx/source/reference/effects_on_pv_system_output.rst

@@ -0,0 +1,13 @@
+.. currentmodule:: pvlib
+
+Effects on PV System Output
+===========================
+
+.. toctree::
+   :maxdepth: 2
+
+   loss-models
+   snow
+   soiling
+   shading
+   spectrum

docs/sphinx/source/reference/effects_on_pv_system_output/index.rst

@@ -0,0 +1,10 @@
+.. currentmodule:: pvlib
+
+Loss models
+-----------
+
+.. autosummary::
+   :toctree: ../generated/
+
+   pvsystem.combine_loss_factors
+   pvsystem.dc_ohms_from_percent

docs/sphinx/source/reference/effects_on_pv_system_output/loss-models.rst

@@ -0,0 +1,11 @@
+.. currentmodule:: pvlib
+
+Shading
+-------
+
+.. autosummary::
+   :toctree: ../generated/
+
+   shading.masking_angle
+   shading.masking_angle_passias
+   shading.sky_diffuse_passias

docs/sphinx/source/reference/effects_on_pv_system_output/shading.rst

@@ -0,0 +1,12 @@
+.. currentmodule:: pvlib
+
+Snow
+----
+
+.. autosummary::
+   :toctree: ../generated/
+
+   snow.coverage_nrel
+   snow.fully_covered_nrel
+   snow.dc_loss_nrel
+   snow.loss_townsend

docs/sphinx/source/reference/effects_on_pv_system_output/snow.rst

@@ -0,0 +1,10 @@
+.. currentmodule:: pvlib
+
+Soiling
+-------
+
+.. autosummary::
+   :toctree: ../generated/
+
+   soiling.hsu
+   soiling.kimber

docs/sphinx/source/reference/effects_on_pv_system_output/soiling.rst

@@ -0,0 +1,12 @@
+.. currentmodule:: pvlib
+
+Spectrum
+--------
+
+.. autosummary::
+   :toctree: ../generated/
+
+   spectrum.spectrl2
+   spectrum.get_example_spectral_response
+   spectrum.get_am15g
+   spectrum.calc_spectral_mismatch_field

docs/sphinx/source/reference/effects_on_pv_system_output/spectrum.rst

@@ -11,9 +11,9 @@ API reference
    solarposition
    clearsky
    airmass_atmospheric
-   irradiance
-   pv_modeling
-   effects_on_pv_system_output
+   irradiance/index
+   pv_modeling/index
+   effects_on_pv_system_output/index
    tracking
    iotools
    forecasting