Platform hierarchy launch test re-enabled and various configuration updates

- several important updates related with platform configuration
- various interim hacks removed
- on_quit implemented for graceful termination of platform agent, including quick termination of monitoring greenlets
- simulator: added a couple of parameters in preparation for next update of parameter dictionary to start testing multiple parameters
- important test refactoring to leverage a common set-up for the two major integration tests
- includes updates in agent_configuration_builder by Ian
- removed obsolete test files 
- updated TESTED_DOC in ion_loader to use attribute specifications for test platform

Testing:
- typical syncing with coi-services mainline as of evening Fri 3/15
- all platform agent-related unit and integration tests OK. No more skipped tests except for very preliminary CGSN code
- UI testing: ion-ux synced and usual platform agent commanding in the UI OK

There's still work to do in general, but this is an important update.
Please review and merge at your earliest.