Fixed header visibility of all the new/moved headers (they were not marked as public).

Added a "kCMISLibraryVersion" constant that can be used to retrieve the version of the library being used.

git-svn-id: https://svn.apache.org/repos/asf/chemistry/objectivecmis/trunk@1608693 13f79535-47bb-0310-9956-ffa450edef68