methods based on the architecture diagrams; copied null capability
implementation from wksp0

wf_monitor to use new amqp_helpers setup; updated wf_monitor tests;
updated WorkflowEventSchema to accept a string in the timestamp field
instead of a datetime (we could probably change this, but this is how
it's set up for now)

originally going to use a singleton pattern but ran into issues with
that)

Merge branch 'SSA-6320-workflow-service' of https://open-bitbucket.nrao.edu/scm/ssa/data into SSA-6320-workflow-service

Merge branch 'SSA-6320-workflow-service' of https://open-bitbucket.nrao.edu/scm/ssa/data into SSA-6320-workflow-service

all necessary fields have been updated to reflect naming changes

Hopefully final changes to setup.py files regarding package name changes; renamed a amqp_helpers dir to channels

Merge branch 'SSA-6320-workflow-service' of https://open-bitbucket.nrao.edu/scm/ssa/data into SSA-6320-workflow-service

Made amqp_helpers directory structure match the other subprojects. Made some small changes to monitor.py and test_monitor.py

Merge branch 'SSA-6320-workflow-service' of https://open-bitbucket.nrao.edu/scm/ssa/data into SSA-6320-workflow-service

Added event_catcher.py with some notes on design and amqp_helpers.py, which contains some helper functions for AMQP-related procedures