overrides: Add fish version 2.0.0.

Now let's try another shell, shall we?

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
fish: Correctly wrap Python tools.

This inserts pythonPath directly into the corresponding script file instead of
using wrapPythonPrograms or wrapProgram. It doesn't make sense to use a sh/bash
script in order to load a fish tool, right?

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Move over from TKabber to Gajim.

This not only patches the desired configuration into Gajim itself but also
enforces a specific GTK+ theme to be used for Gajim only. The main reason for
that is to mimic the look of my previos TKabber theme and configuration.

For the gory details, have a look at the patch. Basically we just use the config
from the nix store as a default configuration file and only add changed lines to
the configuration in the home directory. That way we can still play around with
options while not killing our base configuration. If we want to make something
permanent, we can just move it into the nix config.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
gajim: Convert gajim.config into a Nix attrset.

This should bring us to the point where it's easy to kill off some repetition in
the config file by defining functions for those repetitive values.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>