Updates to pyutilib.misc.config

[jsiirola]

Fixes: #N/A

Summary/Motivation:

This PR adds some long-overdue documentation for the ConfigValue / ConfigList / ConfigDict system. As part of this, it resolved some bugs and begins the process to rename ConfigBlock to ConfigDict (both names are currently supported). The documentation was confirmed to build and pass doctests (using the Pyomo Online Docs harness).

Changes proposed in this PR:

• Rename ConfigBlock to ConfigDict
• Add ConfigDict.declare_from() method
• Resolve a bug involving ConfigDict.set_value() and __getitem__ for derived ConfigDict classes
• Add a visibility option to display()
• Add lots of documentation

Legal Acknowledgement

By contributing to this software project, I 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.

[coveralls]

Coverage decreased (-0.08%) to 60.993% when pulling f129c2e on jsiirola:config-updates into 0fd5f24 on PyUtilib:master.

[codecov-io]

Codecov Report

Merging #88 into master will decrease coverage by 0.09%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #88      +/-   ##
==========================================
- Coverage   63.10%   63.00%   -0.10%     
==========================================
  Files          87       87              
  Lines        8800     8824      +24     
==========================================
+ Hits         5553     5560       +7     
- Misses       3247     3264      +17     

Impacted Files	Coverage Δ
pyutilib/misc/config.py	92.51% <66.66%> (-2.23%)	⬇️

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[michaelbynum]

I love it!