Add support for profile pics to the bundled app

[miskfi]

The standard (python files run from command line) distribution allows adding profile pictures to the output, if the users adds the picture to a certain folder. We need a way to allow for this in the bundled app - probably have the user select a folder with the profile pictures just like he selects the folder with the messages. I would probably like to combine it with #88 and include this in the settings menu.

[stepva]

depends on #88 probably