Remove manag_.groovy

This was an experiment that was not adopted.

Retaining just creates confusion.

For reference, these are the commits related to the file:

o    68d4d22f kk [JENKINS-8446] it's better to let those directories setting be a part of JENKINS_HOME rather than being independent configuration properties, since they aren't orthogonal.
:\
: o  82917200 kk making it more type-safe
: |
: o  8c7c1c62 kk this file is now auto-generated
:/
o  61768cc0 kk not specifying the file extension so that different pieces can be implemented by different view technologies
|
o  12ad3b02 kk replaced i18n by '_' since it shows up a lot.
:
o  00bc3298 kk experimental re-write of the "manage Jenkins" view by Groovy
|
~

core/src/main/resources/jenkins/model/Jenkins/manag_.groovy

-package hudson.model.Hudson
-
-l=namespace(lib.LayoutTagLib)
-t=namespace(lib.JenkinsTagLib)
-st=namespace("jelly:stapler")
-
-def feature(String icon, String href, String title, Closure body=null) {
-    t.summary(icon:icon, href:href, iconOnly:true) {
-        div(class:"link") {
-            a(href:href, title)
-        }
-        div(style:"color:gray; text-decoration:none;",body)
-    }
-}
-
-l.layout(title:_("Manage Jenkins"),permission:app.ADMINISTER) {
-
-    st.include(page:"sidepanel")
-    l.main_panel {
-        h1(_("Manage Jenkins"))
-
-        if (my.isCheckURIEncodingEnabled()) {
-            script """
-                var url='checkURIEncoding';
-                var params='value=\u57f7\u4e8b';
-                var checkAjax=new Ajax.Updater(
-                  'message', url,
-                  {
-                    method: 'get', parameters: params
-                  }
-                );
-            """
-            span(id:"message")
-        }
-
-        app.administrativeMonitors.each { am ->
-            if (am.isActivated() && am.isEnabled())
-                st.include(it:am, page:"message")
-        }
-
-        st.include(page:"downgrade")
-
-        table(style:"padding-left: 2em;",id:"management-links") {
-            feature("setting.gif", "configure", _("Configure System")) {
-               raw(_("Configure global settings and paths."))
-            }
-            // TODO: more features
-
-            app.managementLinks.each { m ->
-                if (m.iconFileName==null)   return;
-                feature(m.iconFileName, m.urlName, m.displayName) {
-                    raw(m.description)
-                }
-            }
-
-            if (app.quietingDown) {
-                feature("system-log-out.gif","cancelQuietDown",_("Cancel Shutdown"))
-            } else {
-                feature("system-log-out.gif","quietDown",_("Prepare for Shutdown")) {
-                    raw(_("Stops executing new builds, so that the system can be eventually shut down safely."))
-                }
-            }
-        }
-    }
-}
\ No newline at end of file