devref: virtual machine states and transitions

The diagrams were hard to read and update. Replaced them with
simplified diagrams and tables. I used the content as is. I looks
inconsistent to me, but should now be easier to change.

Partially implements: blueprint devref-refresh-liberty

Change-Id: I707e1a6ab69ef44448b66e8be007307b5d73eb06

doc/source/conf.py

@@ -35,6 +35,7 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.graphviz',
               'oslosphinx',
               "ext.support_matrix",
+              'sphinxcontrib.seqdiag',
               ]
 
 todo_include_todos = True

test-requirements.txt

@@ -16,6 +16,7 @@ python-ironicclient>=0.6.0
 python-subunit>=0.0.18
 requests-mock>=0.6.0 # Apache-2.0
 sphinx!=1.2.0,!=1.3b1,<1.3,>=1.1.2
+sphinxcontrib-seqdiag
 oslosphinx>=2.5.0 # Apache-2.0
 oslotest>=1.5.1 # Apache-2.0
 testrepository>=0.0.18