[documentation] return of most popular handbook pages list

[Addison Berry]

For those that were wondering, the old Most popular handbook pages  
list (handbook/most-popular-pages) stopped working earlier this year  
because d.o stopped using the stats module from which we were  
programmatically pulling the list. After a bit of back and forth, the  
list is back in a different form. I am manually compiling a list of  
the top 25 for each month from the server log AWStats. I have added  
the link back to the Documentation links block as well. Enjoy.

- Addi (add1sun)
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