client: Made several usability changes to xtfsutil:

- Catching invalid command line parameters now.
- -l displays the list of suitable OSD UUIDs and their addresses.
- Workaround for -a with left out default value "AUTO" (see issue 219, works only if the specified file exists)
- When setting replica policy to none, --replication-factor no longer mandatory (fixes issue 217).
- Added checks for supplementary options like --full or --value to make sure they are only used in conjunction with their required primary parameters (like -a, --set-drp or --pattr).

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2723 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534