[dev] Disable sidebar by default

[Chuck Hagenbuch]

Quoting Michael M Slusarz <slusarz at horde.org>:

> I'm thinking we need to rewrite Horde_Block for the sidebar; since  
> portal blocks/widgets aren't anything close to the same as sidebar  
> block/widgets.  This code needs to be H4'ified anyway, and should  
> probably be moved to Horde_Core.
>
> Then each individual sidebar block could indicate whether its  
> results can be cached or not for each session.  Example: if folder  
> polling is disabled in IMP, we could used cached results to display  
> the sidebar widget (folder creation/deletion could trigger a manual  
> deletion of the cached result so that the folder list is accurately  
> displayed).

For IMP the main issue is the INBOX unread count, but in general that  
sounds right. I agree that sidebar widgets should be separated from  
portal blocks (not sure the exact right terms there yet) - that was a  
stretch at the start.

-chuck