Merge pull request #107 from aronr/CSPACE-6199

CSPACE-6199: Allow sparse overriding of admin settings in settings.xml.
CSPACE-6204,CSPACE-6207: Integrated Ray's contribution of a separate XmlMerge properties file for the per-tenant settings.xml file, splitting this off from the general XmlMerge properties file. Added a terms-used block to the latter properties file, also a UCB contribution. Added explanatory comments to each of the two properties files.
CSPACE-6024: Clarified comment describing use of XPaths in XmlMerge.
CSPACE-6024: Additional clarification of comments.
Merge pull request #108 from aronr/CSPACE-6204

CSPACE-6204,CSPACE-6207: Split off XmlMerge properties related to settings file. Add terms-used merge rule.