remove unused import
merge upstream/master
initial integration of code for rollup status handling and updates based on
corresp statuses in  children. A complete test with a small platform
hierarchy (no instruments yet) with various cases already implemented:
test_platform_status.py
merge upstream/master
correct comment
consider the new PA's aparams in test_capabilities
fix typo (no change in effect but consistent with the idea of using the other
 child)
fix maurice's comment ;-)
Merge pull request #871 from carueda/platform_agent_R2C4

integration of rollup status handling in the platform agent.