Reorder, aligning with antlib.xml.

Merged r1643738 from tomcat/tc8.0.x/trunk (r1643733 from tomcat/trunk).

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1643740 13f79535-47bb-0310-9956-ffa450edef68
Add "sessions" command from antlib.xml

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1643741 13f79535-47bb-0310-9956-ffa450edef68
Fix http://issues.apache.org/bugzilla/show_bug.cgi?id=57261
Backport Diagnostics class, /vminfo and /threaddump command in Manager application and their Ant tasks from Tomcat 8.
Update documentation.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1643750 13f79535-47bb-0310-9956-ffa450edef68
For http://issues.apache.org/bugzilla/show_bug.cgi?id=57261
Remove Diagnostics methods that are not used by Tomcat 7, reduce visibility. (Followup to r1643750)

If you see any way to use those methods, feel free to revert this commit.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1643754 13f79535-47bb-0310-9956-ffa450edef68