* Upgrade modules to use Tools 1.6-SNAPSHOT and introduce a platform.tools.version property in XEM and XE modules to manage the version of Tools to use in a single location.

* XEM is using 1.5 since we it's going to be released soon and it'll be released with 1.5

* I haven't touched Curriki since I'd prefer if David manages the curriki build since I don't fully control curriki's build process (there are some other scripts) and since Curriki development is critical and cannot fail. Note for David: when the disk is full on the maven.xwiki.org machine, we'll need to make up some space by cleaning up the SNAPSHOT repository and thus 1.5-SNAPSHOT will disappear at that time, causing a build failure if Curriki's modules are not updated to use 1.5 or 1.6-SNAPSHOT. Also note that for XEM and XE I have introduced a property to manage the Tools version in a single place.

git-svn-id: https://svn.xwiki.org/svnroot/xwiki/xwiki-platform/xwiki-tools/trunk@5010 f329d543-caf0-0310-9063-dda96c69346f