These are some explorations to create a tricycle that can be controlled from ros.
To build the plugin create a build directory and make everything with
mkdir build
cd build
cmake ..
make
The plugins should now be build. To let Gazebo know where the plugins are, the directory has to be added to the plugin path
export GAZEBO_PLUGIN_PATH=`pwd`:$GAZEBO_PLUGIN_PATH
Gazebo can now be started. To see the stderr from the plugins, use gazebo --verbose to start Gazebo.