several updates and better alignment with standard mechanisms

Also includes some refactoring of the int tests to faciliate additional tests, for example with further interaction with instruments, in particular new test : test_platform_instrument.py:

    bin/nosetests -sv ion/services/sa/observatory/test/test_platform_instrument.py:Test.test_platform_with_instrument_streaming

*NOTE*  All unit and int  platform tests passing.  Please merge ASAP.