Problem
Rename module name singlediode_methods.py and refactor pvsystem.singlediode

• singlediode_methods.py is a long name for a module
• the suffix "methods" is ambiguous, superfluous, and not descriptive
• the other modules have meaningful names that correspond loosely to the modeling steps described at Sandia PVPMC
• there needs to be a discussion regarding possibly refactoring pvsystem.singlediode
  • having a module shadow a method from a different module might be confusing or maybe it's not a problem?
  • has there already been discussion on breaking singlediode up, refactoring, or renaming it?

Proposed Solution
Rename module singlediode_methods.py to just singlediode.py and consider refactoring pvsystem.singlediode

1. rename the module from singlediode_methods.py to just singlediode.py
2. change all references in the code where appropriate
3. change all references in the comments and documentation where appropriate
4. start a discussion on the repercussions to the singlediode() methods in pvsystem.py

alternatives

• rename the module something else like dc_energy.py, pvmodules.py, or pvcells.py
• do nothing
• rename the module to singlediode.py and leave pvsystem.singlediode() alone
• rename the module to singlediode.py and move pvsystem.singlediode() to singlediode.singlediode() which is a more established pattern, right?

Additional context

• this is a follow on to ENH: implementing pvsyst recombination loss current for CdTe and a:Si #504
• comments in move lambertw to singlediode-methods module #497
• also related to singlediode is slow #408, ENH: add methods and tests for a explicit IV curve calculation of single-diode model #409, and Single diode model helper function to wrap Lambert w and other methods #410