NEXUS-6134 - remove 'httpclient' logger, we no longer ship with httpclient 3x
NEXUS-6134 - make sensible defaults for org.apache.http loggers to make debugging outbound headers easier

user will need to simply change org.apache.http to DEBUG now, should they wish to debug outbound headers

Confirmed that changing ROOT logger to DEBUG will not print wire...

(reformatted this to match nexus-2.7.x branch)