[PATCH] Support for :file command

Hi all, In attachment is a patch to support correct ':file' command, that should provide basic information about file. Current implementation in Evil is alias to ':files', which will incorrectly display available buffers. I tried to match Vim's output as much as possible. Also, I'm not sure does Evil already provides some facilities for querying file informations so I used Emacs api. Feel free to adjust it :) Please let me know if something breaks. PS: should I fill issue for this request? Regards, Sanel