Usage of condor within containers

[kpedro88]

This PR introduces two methods to use condor while inside containers:

1. Using pipes to run condor commands on the host node while inside a container
2. Importing the host condor configuration into the container and installing the python bindings locally

Known issues:

• The automatic OS detection on cmslpc does not know about containers, so you have to specify the desired OS and/or container manually in the job description file.
• Support for other (non-cmslpc) clusters is not included yet.