New block-based live migration

The ops guide originally discouraged block-based live migration.
However, there is now an improved implementation of block-based
live migration, so the wording has been changed to no longer
actively dissuade people from using it, while acknowledging that
the authors don't have firsthand experience with it.

Change-Id: Ie9ec49aa3b31f41b5e65087cac5037c78c021c69
Rewrites the Basic Install Guide for Grizzly

Fixes common for command.

Change-Id: I373439dc790fb430f834de502d7bc790a2a495e7
Merge "New block-based live migration"
Merge "Rewrites the Basic Install Guide for Grizzly"