apt-get apt-file : Working out what package a file belongs to.

Install apt-file

sudo apt-get install apt-file

Update it

sudo apt-get update

Run it

sudo apt-get search <filename>

The last line will result in a list of files and their related package

For installed apps/packages you can use

dpkg -S <filename>

 
This however will not show you config files created AFTER the package was installed.