[suggestion] Fortify / set watch

Now that we can fortify units, It would be nice if on the following turns you would have an option to set a watch.  Doing so would increase your sight radius by the movement of the units fortifying.  Would represent patrolling that would naturally occur.  The button for fortify could turn into a tower symbol or something, and if chosen a little wood platform could be added to the palisade graphic.

It should probably cost some materials 3-5 or so.