* src/virsh.c (cmdPoolStart, cmdStart): Change hard-coded
vshCommandOptDomainBy string argument to match just-changed
option name.  Cole Robinson reported that "virsh start" was
broken and provided that part of the fix.
Bug introduced by yesterday's "virsh.c: tweak options to produce
more accurate help".
* tests/start: New file.  Test for the above fix.
* tests/Makefile.am (test_scripts): Add start.

* src/virsh.c: Adjust some vshCmdOptDef command option flags
to improve auto-generated help command syntax.

* src/virsh.c: ... now that info is generated.

* src/virsh.c: Now, every command must have a "desc" string,
even if it has zero length.  Mark these, so they'll be filled in.

* src/virsh.c: Also, diagnose extra arguments after --help (-h).

Daniel