A new environment variable (FABRIC_LOGGING_SPEC) has been
added, and support for the CORE_LOGGING_LEVEL and log module
overrides has been removed.

FAB-12487 #done

Change-Id: Ia8d72b3b41dd5ac9e37747209fdc51c9014b2811
Signed-off-by: Saad Karim <skarim@us.ibm.com>
Signed-off-by: Will Lahti <wtlahti@us.ibm.com>