Add section information to settings
Add section information to settings

All settings now contain a `_section` property which has the section name
as value. This makes it possible to determine e.g. whether you are in the
access or the load phase.

From now on properties with a leading underscore are ones that are not
specified in the configuration file, but are generated in some other ways.

Change-Id: I437f39abd51be6007c80460e7a82aece8c16c7cf
Reviewed-on: http://review.couchbase.org/52831
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Reviewed-by: thomas anderson <5f50a84c1fa3bcff146405017f36aec1a10a9e38@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

couchbase/perfrunner,pavel-paulau/perfrunner,EricACooper/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,dkao-cb/perfrunner,mikewied/perfrunner,couchbase/perfrunner,dkao-cb/perfrunner,EricACooper/perfrunner,vmx/perfrunner,EricACooper/perfrunner,couchbase/perfrunner,pavel-paulau/perfrunner,EricACooper/perfrunner,mikewied/perfrunner,pavel-paulau/perfrunner,pavel-paulau/perfrunner,couchbase/perfrunner,couchbase/perfrunner,vmx/perfrunner