refactor ModelChain, add pvwatts, singlediode, aoi, and more options (#194)

* implement dc_model, ac_model kwargs with property decorators

* use public instead of private methods

* clean up

* whitespace

* pep8

* add aoi, spectral, temp model controls. add pvwatts. needs more tests

* add losses and a few tests

* implement log lambertw calculation in v_from_i

* add test

* more robust

* get realistic singlediode test working

* add note to whatsnew

* add issue note to test

* add tests for user supplied functions

* more tests

* add decorators

* update whatsnew

Author: wholmgren

docs/sphinx/source/package_overview.rst

@@ -200,6 +200,10 @@ objects to accomplish our system modeling goal:
     @savefig modelchain-energies.png width=6in
     plt.ylabel('Yearly energy yield (W hr)')
 
+See Will Holmgren's
+`ModelChain gist <https://gist.github.com/wholmgren/3fabacd3003c2a549b420b5e79f55e95>`_
+for more discussion about new features in ModelChain.
+
 
 Object oriented (LocalizedPVSystem)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

docs/sphinx/source/whatsnew/v0.4.0.txt

@@ -54,6 +54,11 @@ Enhancements
 * pvsystem.singlediode can now calculate IV curves if a user supplies
   an ivcurve_pnts keyword argument. (:issue:`83`)
 * Includes SAM data files in the distribution. (:issue:`52`)
+* ModelChain now implements SAPM, PVWatts, Single Diode and user-defined
+  modeling options. See Will Holmgren's
+  `ModelChain refactor gist <https://gist.github.com/wholmgren/3fabacd3003c2a549b420b5e79f55e95>`_
+  for more discussion about new features in ModelChain.
+  (:issue:`143`, :issue:`194`)
 
 
 Bug fixes