Refactor to clean up names.
Merge pull request #1336 from brendandburns/privilege

Refactor to clean up names.
Fix etcd install instructions.
Adds support for attaching GCEPersitentDisks

Adds GCEPersistentDisk volume struct

Adds gce-utils to attach disk to kubelet's VM.

Updates config to give compute-rw to every minion.
Adds GCEPersistentDisk to API
Adds ability to mount attached disks
Generalizes PD and adds tests.

PD now uses an pluggable API interface.

Unit Tests more cleanly separates TearDown and SetUp
Modify boilerplate hook to omit build tags
Adds Mounter interface; mount is now built by OS
TearDown() for PD now detaches disk on final refcount
Un-generalized PD; GCE calls moved to cloudprovider