Remove trailing slashes

SEO guidelines best
practices say you should not serve both the trailing slash version +
the regular version at the same time [1]. One should be a permanent
redirect to the other. In our case, the client would like all trailing
slashes to be removed, like so:

http://www.example.com/news/
redirects to
http://www.example.com/news

It's quite easy to implement this by adding a rule in the url rewriter
plugin like so:
Rewrite From
**/
Rewrite To
$1

In the website this works great. The problem is that suddenly the
channel manager brakes with a null pointer exception [2]. There's no
way I see how to exclude channel manager from the URL rewriter rule,
unless rewriting to using regular expressions and adding something
like (?!\/_cmsinternal).

It would be a lot better to resolve this in the HST. Maybe we should also make lowercase an option. I'd be happy to create a separate issue for that.

1: http://googlewebmastercentral.blogspot.com/2010/04/to-slash-or-not-to-slash.html
2: An error has occurred, sorry for that.
java.lang.NullPointerException: null
Failed to instantiate plugin class
'org.onehippo.cms7.channelmanager.ChannelManagerPerspective' for
wicket id 'service.tab' in plugin
'home.cluster.cms-static.plugin.channelManagerLoader.cluster.hippo-channel-manager.plugin.channel-manager-perspective'
(JcrPluginConfig:/hippo:configuration/hippo:frontend/cms/hippo-channel-manager/channel-manager-perspective)