Allow project-specific LabelTypes in ReviewCommand

Preserve the old site-global options by using label names from
All-Projects. Allow custom/project-specific label names with
--label=My-Label=N, which override the old-style options, if present.

When we have project-specific labels, this means the help text will
include e.g. --verified even if that is removed or has different value
in the relevant projects; the command will then fail when the server
actually tries to apply the review score.

Change-Id: I915399556e9e977b36e996071ff0346f76bc0ff5

Documentation/cmd-review.txt

diff --git a/Documentation/cmd-review.txt b/Documentation/cmd-review.txt
index 513bc6e..d7fb0f7 100644
--- a/Documentation/cmd-review.txt
+++ b/Documentation/cmd-review.txt
@@ -17,6 +17,7 @@
   [--publish]
   [--delete]
   [--verified <N>] [--code-review <N>]
+  [--label Label-Name=<N>]
   {COMMIT | CHANGEID,PATCHSET}...
 
 DESCRIPTION
@@ -94,10 +95,14 @@
 
 --code-review::
 --verified::
-	Set the approval category to the value 'N'.  The exact
-	option names supported and the range of values permitted
-	differs per site, check the output of --help, or contact
-	your site administrator for further details.
+        Set the label to the value 'N'.  The exact option names
+        supported and the range of values permitted differs per site,
+        check the output of --help, or contact your site administrator
+        for further details.  These options are only available for these
+        built-in labels; for other labels, see --label.
+
+--label::
+        Set a label by name to the value 'N'.
 
 ACCESS
 ------