Add the Check for Modification command

[DavidGerva]

Hi, in my workday I use a lot this "Check for modification" operation in Tortoise SVN. This is an "enhanced" Diff view. It works generally with a directory and show you every modified file in that directory.

I developed in the TortoiseSVN plugin for my use this "CheckModification" function both with the right-click on a file/directory in the left bar and in the "scroll-down" menu. If you have a file in your view and you execute a "CheckModification" command you'll obtain a dialog with every modified file of the directory in which you're working.

I don't know if this can be useful for you, but I thought it could be better propose it directly with a pull req. If you think this is useful for someone else (than me) the work is done. (I hope... complete.)

Thank you! David