Enable publication of coverage results from Jenkins

[jsiirola]

Fixes #46.

Summary/Motivation:

This updates the Jenkins builds to use the same coverage approach/configuration as is used by Travis and Appveyor. Separately, the Jenkins builds have been updated to push coverage results to Codecov.

Note that implementing this requires a patched version of codecov, see codecov/codecov-python#187.

Changes proposed in this PR:

• Update Jenkins driver touse the .coveragerc file to configure coverage
• Update the Jenkins driver to enable collecting coverage statistics for subprocesses
• Update the Appveyor driver to get coverage for the pyomo downloaders
• Clean up the Appveyor driver to reduce the number of calls to "conda install"

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.

[codecov-io]

Codecov Report

Merging #842 into master will decrease coverage by 0.55%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #842      +/-   ##
==========================================
- Coverage   66.92%   66.37%   -0.56%     
==========================================
  Files         422      461      +39     
  Lines       67457    71638    +4181     
==========================================
+ Hits        45148    47547    +2399     
- Misses      22309    24091    +1782

Impacted Files	Coverage Δ
pyomo/network/foqus_graph.py	90.37% <0%> (-0.24%)	⬇️
pyomo/contrib/pynumero/examples/feasibility.py	0% <0%> (ø)
pyomo/pysp/scenariotree/server_pyro_utils.py	0% <0%> (ø)
...t/examples/semibatch/semibatch_parmest_parallel.py	0% <0%> (ø)
pyomo/solvers/plugins/testdriver/model.py	0% <0%> (ø)
pyomo/contrib/pynumero/examples/sensitivity.py	0% <0%> (ø)
pyomo/pysp/plugins/interscenario.py	0% <0%> (ø)
pyomo/util/diagnostics.py	0% <0%> (ø)
.../examples/reactor_design/reactor_design_parmest.py	0% <0%> (ø)
pyomo/contrib/pynumero/examples/derivatives_gas.py	0% <0%> (ø)
... and 84 more

---

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[jsiirola]

This is ready to review. The apparent drop in coverage is because codecov found several new files (totaling 4400 lines) that previously had been completely skipped. hat increased outweighed the additional 2500 lines of code that were exercised.

[blnicho]

I think this looks pretty good but you left in quite a few commented lines of code which I think should either be removed or explained for future reference.

[blnicho]

Is there a reason you left these commented lines in?

[jsiirola]

I mostly left them in as breadcrumbs for "future me" / @whart222, when we are going through and trying to remember how things "used to work", especially if we find that this change breaks other Jenkins builds (apart from the ones supporting PR/master testing). I added a comment to this effect.

[blnicho]

I think this looks fine.