Smiley packs

Here is the first implementation of smileypacks (https://github.com/nurupo/ProjectTox-Qt-GUI/issues/49).

I moved the smile/desimle functions the the new smileypack class. This class also contains functions to create a pack from a theme-file. New packs are located in the users settings directory. On my linux it's: `~/.config/Qt GUI for Tox/smileys`.

The smileypack mechanism supports **emoij**. There are two build-in packs: the already existing default pack and a emoij pack. For systems, which don't supporting Unicode 6.1 (like WinXP), I included the "DejaVu Sans" font.
If the user has selected a classic smiley pack, incoming emoij will converted to text and then to the smiley image from the pack.

I also wrote a new algorithm for the "smile" function. The existing function had a problem with "smileys in smileys". E.g. `]:)` and `:)`. Because of the `:)` came at first in the hash, the evil was translated to `]` `:)`. That's fixed now.