packaging: Updated user guide:

- Added section on C++ and Java libxtreemfs.
- Removed last fragments referring to xtfs_vivaldi.
- Minimal corrections in the Hadoop Quickstart section.
- Minor spelling fixes.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@3145 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534