SW-693: Swap ToBus/FromBus broker/options parameters to make overriding broker easier (common) than overriding options (uncommon)

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

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.

SW-44: moved the integration part of the rebuild_resource_usages* method into a seperate method, for later reusage in handling new/old claim.

SW-44: major refactoring/improvement of rebuild_resource_usages_from_claims_for_resource_of_status using a new resource_usage_delta table. Much simpler code, less exceptions and odd cases.

SW-44: minor tweaks in test. The test currently fails on a bug in the resource usages. For that bug I added special test test_20181108_bugfix_resource_usages to t_radb_functionality.py to prove it. First, I'll fix that resource_usage bug, and then continue on the performance improvements.

SW-44: found bug during performance testing. added special test test_20181108_bugfix_resource_usages to t_radb.py to prove it. Renamed t_radb.* to t_radb_functionality.* to make a better distinction with t_radb_performance.py

SW-44: remove obsolete claims once a task ends. This reduces the resource_claim and resource_usage tables significantly, speeding up overall performance.