Moved doxygen related files to Documentation/ and removed old script files.

The setup and corresponding scripts in base are not up-to-date since some time.
Use the devguide guide instead: http://docs.opengeosys.org/docs/devguide
Merge pull request #468 from bilke/scripts-cleanup

scripts-folder cleanup
Require minimum gcc version to be 4.8.

This version supports all of the used c++11 features.
Install GCC 4.8.1 on travis.

Instructions taken from http://askubuntu.com/questions/271388/how-to-install-gcc-4-8