Upgrade gRPC and PySide Python dependencies.

[bcipriano]

Link the Issue(s) this Pull Request is related to.
Fixes #755, #784

Summarize your change.
Upgrading both dependencies to a new version as both are quite old at this point and not supported in newer Python versions.

• New PySide gets rid of the qApp shortcut, so I add a line into CueGUI and CueSubmit to create it. This avoids needing massive code changes in both GUI apps.
• Newest gRPC that supports Python 2 does not publish wheels anymore for newer Python versions, so we need to split that dependency to use different versions on Python 2 and 3.
• In the new PySide signals are recognized as functions, which causes lint issues. Most of the changed lines in this PR are due to disable lint checks on signals, as lint isn't able to detect the signal members such as connect.

[bcipriano]

Unfortunately, the older dependency versions we're currently using are now completely broken for me -- can't create a new virtualenv on my mac workstation. So this is now blocking a new release, and I need to merge it ASAP.

I've tested this out on mac/windows/linux and don't see any issues.