Improve documentation

[kinverarity1]

Describe the bug
The JSON web service methods are too prominent in the documentation. The focus should instead be on (1) what are the bulk CSV/pandas DataFrame methods and (2) what data they return.

To Reproduce
Read the docs and be confused :-)

Expected behavior
Read the docs and be enlightened :-)

Screenshots
N/A

Desktop (please complete the following information):

• OS: N/A
• Python version: N/A
• python-sa-gwdata version: 0.10

Additional context
N/A