Adds version status to limit issue assignments (#1245).

Available version statuses are:
* open: no restriction
* locked: can not assign new issues to the version
* closed: can not assign new issues and can not reopen assigned issues

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3020 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/fixtures/versions.yml

@@ -7,6 +7,7 @@ versions_001:
   id: 1
   description: Beta
   effective_date: 2006-07-01
+  status: closed
 versions_002: 
   created_on: 2006-07-19 21:00:33 +02:00
   name: "1.0"
@@ -15,6 +16,7 @@ versions_002:
   id: 2
   description: Stable release
   effective_date: <%= 20.day.from_now.to_date.to_s(:db) %>
+  status: locked
 versions_003: 
   created_on: 2006-07-19 21:00:33 +02:00
   name: "2.0"
@@ -23,4 +25,5 @@ versions_003:
   id: 3
   description: Future version
   effective_date: 
+  status: open