Clean up watchers routes declaration.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11342 e93f8b46-1217-0410-a6f0-8f06a7374b81
Use POST/DELETE to watch/unwatch an item.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11343 e93f8b46-1217-0410-a6f0-8f06a7374b81
Don't generate duplicate ids.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11344 e93f8b46-1217-0410-a6f0-8f06a7374b81