This commit fixed some bugs from the last commit as well as some general
changes and fixes of some old bugs. For overview of all changes please
look inside `CHANGELOG.md`.
This commit adds a GWEN UI style skinning example. It is
certainly not perfect right now (especially windows suck) but
it is probably useful for a general overview. One thing that is
pretty clear for me now is that I need a way to read in a style from
file or memory since manually setting up properties, colors
and images is quite a pain.