Minor fixes per comments from Michael H.

Updated configure-mapr-instance.sh so that the access to GCE metadata
conformed to the lastest standard.
Added lsof to Debian initialization, since we use it so much.
launch-mr-cluster no longer appropriate ... and will just
confuse users.

If needed, we can re-work as a wrapper around launch-mapr-cluster.sh.
Added logic to add MapR user to sudo group if one exists.
Simplifies the operation of the cluster.
Changed default NFS mount behavior for cluster; simply mount
mfs://mapr to /mapr to allow uniformity between shell-level and
hadoop-level access to files.
Access to GCE metadata changed to reflect GA release from Google.
Latest GCE tools will throw errors for non-existent files ... so
passing "metadata_from_file" arguments need to be constructed more
carefully.

Added support for automatic authorization of access to Google Storage
buckets.
New support for Google Cloud Storage configuration.
Updated with latest details on new Google metadata server specification.