[dev] Disable sidebar by default

[Michael M Slusarz]

The new sidebar code is good now that we got rid of frames.  But it is  
bad because it has to be regenerated every time a page is loaded.   
This is quite a bit of extra load.  Enough so that I wonder if sidebar  
should be disabled by default.  Alternatively, we need to do some sort  
of caching of the tree so that it does not need to be rebuilt on every  
page click.  Maybe do absolute time caching (e.g. we only rebuild the  
tree every 'refresh_time' minutes - when the page is loaded, the next  
refresh will be the difference between the next refresh time and the  
current time).

michael