Providing Memory Snapshots for Instances

Develop the capability to create and revert memory snapshots for instances.
Currently nova can create image snapshots, however it only captures the
state of the file system, not the state of the memory. This topic has been
proposed in previous versions, yet none of them have been fully integrated into
openstack. There are several use cases for taking snapshots of memory,
processor states, disks. and other devices. By developing a take/restore
snapshot chaining capability, users will be able to quickly return a particular
virtual machine state instead of booting a new instance, thus saving more time
while testing. Note, this does not necessarily have to replace the current
snapshot functionality; it would extend the capability.