Adding Sphinx examples for each of the QA modules in the package.

[kperrynrel]

Add Sphinx documentation to illustrate the value of each of the following modules, in order:

-clipping
-Data gaps (gaps module)
-Outlier detection and removal (outliers)
-Irradiance
-Day-night masking

Include example data for these modules in the /data/ folder.

[kandersolar]

May be better to have one example per function instead of one example per module to keep them from getting overly lengthy. Also, we're not using it currently, but it's easy to configure sphinx-gallery to organize examples by topic.

[kperrynrel]

Additional modules to add documentation for:
-orientation
-shading
-weather
-metrics