SW-575: Merged task branch back to Release branch. Allows setting individual weights for multiple beamlets.

We mount now a directory to /opt/slurm that contains executables of
slurm version 17.11.13.  This version is again compatible with the version
that runs on head.cep4.

This branch contains a fix for the lofar-pipeline after the slurm upgrade
on head.cep4.

task SW-575: Add a utility function to convert a string of complex pairs to a list of complex numbers

Task SW-581: Cherry Picked revision 40995 from trunk to release to have the changes in the cobalt_functions.sh in production

This story allows multiple weights to be set with rspctl for an equal amount of beamlets.

SW-35: minor changes after rollout. Only prevent task prescheduled->scheduled state change when not all claims are claimed. Try/except for different versions of psycopg2

Task ROHD-1323: Slight improvement of LBA delays. Note that file is resported, only LBA delays changed.

SW-44: removed timing code, and notices. minor performance improvement in get_max_resource_usage_between

SW-44: major simplification of process_new_claim_into_resource_usages and process_old_claim_outof_resource_usages using the new deltas table. Now the new test_20181108_bugfix_resource_usages passes as well, and preliminary results indicate a performance boost as well.