Add a second action menu to IssuesController#show. (#4331)

Will have the update, log time, watch, copy, etc buttons.  Had to rework
how the watchers button works since it requires a unique DOM id for the
Ajax response.  Also modified the WatchersController to be able to replace
multiple sections of the page, e.g. two Watch links.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3119 e93f8b46-1217-0410-a6f0-8f06a7374b81