Add "Analyze Game at this/current position" menu item

[GoogleCodeExporter]

Usually when I've been using the Analyze Game dialog, I haven't wanted to do 
from the very beginning of the game, but from a certain position. Adding an 
"Analyze Game at This Position" or "Analyze Game at Current Position" menu item 
below the current "Analyze Game" one would be an elegant and easy way to do 
this, I think.

Original issue reported on code.google.com by mattgatto on 4 May 2014 at 10:22

[GoogleCodeExporter]

Another possibility is to add "from" and "to" fields to the dialog as in 
Shredder, with current ply as default "from".

Original comment by gbtami on 5 May 2014 at 8:24