Bug fixes for setting / handling environment variables

[dschristianson]

Correct documentation for setting environment variables
Correct handling of EPA_GEOSERVER_WFS_TIMEOUT_LIMIT value as a numeric

Fixes #205

Type of change

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

How Has This Been Tested?

• Unit tests
• Integration tests
• Test coverage >= 90%
• Flake8 Tests
• Mypy Tests
• Other - manual tests setting various values for EPA_GEOSERVER_WFS_TIMEOUT_LIMIT

Test Configuration

• Python Version: 3.10

PR Self Evaluation

• My code follows the agreed upon best practices
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
  - [ ] I have added tests or modified existing tests that prove my fix is effective or that my feature works
• Existing unit tests pass locally with my changes
  - [ ] Any dependent changes have been merged and published in the appropriate modules
• I have performed a self-review of my own code