QA upgrade script multiple environments #11302

https://trac.openmicroscopy.org.uk/ome/ticket/11302

Modifies the OMERO-qa-upgrade.py script to allow swapping of servers requiring different environments, e.g. replacing an ice33 server with an ice35 one. This script caches some environment variables in a file OMERO_SERVER/omero.envvars after starting the server, and attempts to read these vars back in when stopping the server for an upgrade. This allows `omero admin stop` linked against ice33 to work when the new server is linked against ice35. In principle this should also work for non-ice environment dependencies.

Also deletes the previous server directory and zip.

Testing: see http://hudson.openmicroscopy.org.uk/view/Analysis/job/OMERO-QA-upgrade-example/
If you want to run the job with different ice versions read the job description. Just make sure the ice version and server version match, e.g. ice33/OMERO-merge-develop, ice34/OMERO-merge-develop-ice34, ice35/OMERO-merge-develop-ice35.

Note the above job uses an auxiliary script to set the environment (this will have to be server/config dependent and is not part of this PR), see the Jenkins job config for more information.