CELIX-106: Added global/extern variable for framework logger. Updated log calls to use this logger. (+1 squashed commit)
Squashed commits:
[a529aa2] Started adding FrameworkLogger to be able to override framework logging.

git-svn-id: https://svn.apache.org/repos/asf/incubator/celix/trunk@1557991 13f79535-47bb-0310-9956-ffa450edef68