Add FHS-compliant installation instructions for Linux (fixes #58)
Remove obsolete instructions
Rename OPENDUNGEONS_* variables to use the OD prefix
Rename last OPENDUNGEONS_* variables to use the OD prefix
Add a desktop entry and icons to be installed in the hicolor theme on Linux
Add translation of the desktop file comments: dansk, deutsch and français
Remove useless intermediate OD_*_DEST variables
Link icon dynamically (let the system locate it in the hicolor theme) when the CMAKE_INSTALL_PREFIX is /usr
Merge pull request #204 from akien-mga/linux-install

Add installation instructions for Linux + some distribution bonus (desktop file, icon)