CMake support and Google Test

This patch adds CMake suppport (with Source Groups @Carsten)
![source-groups](https://f.cloud.github.com/assets/2237173/585039/efbc510e-c92d-11e2-9274-dcd066f24906.png)

and a new target called "ogdf-test" for unit testing OGDF (it outputs performance and success data
![gtest](https://f.cloud.github.com/assets/2237173/585045/0b80a020-c92e-11e2-9d91-ed40bd654272.png)