This patch adds new options to the "virsh list" command enabling
filtering of persistent and transient domains along with the option to
print only UUIDs or names of domains instead of printing the table.

Option --name prints domain names (one per line) instead of the default
table. Similarly --uuid prints domain's UUID. The option --table is
an alias for the default behavior.

Aditionally --persistent and/or --transient may be specified to filter
the output of domains.