Flesh out the HA documentation a bit more

Signed-off-by: David Scott <dave.scott@citrix.com>
Start adding some message sequence charts

Signed-off-by: David Scott <dave.scott@citrix.com>
Add a diagram for shutting down a host.

Signed-off-by: David Scott <dave.scott@citrix.com>
HA: add a diagram for HA clean disable

Signed-off-by: David Scott <dave.scott@citrix.com>
HA: add a disable unclean diagram

Signed-off-by: David Scott <dave.scott@citrix.com>
HA: add some description to go with the first few diagrams

Signed-off-by: David Scott <dave.scott@citrix.com>
HA: add some more explanation

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #5 from djs55/more-ha

Flesh out the HA documentation a bit more