interface: Added host round robin osp to GlobalTypes.
server: Added host round robin osd selection policy.
docs: Added description of host round robin osp to xtreemfs userguide.
docs: Updated xtreemfs userguide to latest version from master.
client, docs: Added support of host round robin osp to xtfsutil.
server: Added host round robin policy to build in policies.
Merge pull request #322 from xtreemfs/lkairies-host-round-robin-osp

lkairies host round robin osp