Add appveyor config back for building windows wheels (#2979)
Add appveyor config back for building windows wheels (#2979)

* Add appveyor config back for building windows wheels

With the recent instability and unreliability with azure-pipelines
relying on it to build our windows wheels for the upcoming 0.9 release
doesn't seem to be prudent. Especially when considering our ability to
create reliable portable wheels for a windows environment manually
outside of CI is limited (we've had issues trying to do it manually in
the past). This commit adds back our appveyor config for building wheels
which has worked well for past releases. This way even if azure fails
for us we have a fallback available when we push our release tag.

* Do not merge, verifying it still works

* Revert "Do not merge, verifying it still works"

This reverts commit 285bfbb12cd20a76fcf70eb136047ff0e9e30bd8.

* Upload artifacts even if build fails

* Add back one job so it doesn't sit pending forever

The appveyor ci system doesn't like a config with 0 jobs configured to
run. If no jobs are configured to run it will sit there forever as
pending state. Since we only want to run the wheel build jobs on tags if
we only had the wheel jobs in the config this would result in an
appveyor entry in the checks on github sitting in a pending state
forever. To avoid this problem this commit adds a normal test job that
will run python 3.7 job so something will come back. We can safetly
ignore this job since it's duplicated with with what we run in azure,
but it will at least mean we're not leaving a PR in the pending state
forever.

* Use ps backend for mpl tests

QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py