Fixes NA

Summary/Motivation:

Inspired by #1026, this standardizes across all documentation and code to use import pyomo.environ as pyo rather than as pe.

Changes proposed in this PR:

• Replace import pyomo.environ as pe with import pyomo.environ as pyo

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.