Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=40001

Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=40001
Use POST rather than GET for all operations that are not idempotent
Partly based on a patch suggested by Daniel Naber
Remove the "Are you sure?", partly due to lack of i18n support and since as (based on my recollection) as many people disliked the feature as liked it.
Provides a (very) small measure of CSRF protection but lays the foundation for using a nonce with POST.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@823962 13f79535-47bb-0310-9956-ffa450edef68