Reverted the toolbar.

An hardcoded ui string is a not-so-good idea, especially since the old code was using deprecated StockIDs for the icon.
They were also upscaled, resulting in blurry icons.
Let's just go with this until we have a proper UI mockup or something.
Add settings dialog

Doesn't fully work !!
Needs to implement a few other action listeners, methods, and error checks.
settings.glade must be in the same directory as the executable too.