Hector description: added files and loader

.gitignore

CMakeLists.txt

...description/meshes/quadrotor/blender/quadrotor_base.blend

hector_description/meshes/quadrotor/quadrotor_base.dae

hector_description/meshes/quadrotor/quadrotor_base.stl

hector_description/package.xml

hector_description/robots/quadrotor_base.urdf

hector_description/robots/quadrotor_base.urdf.xacro

hector_description/robots/quadrotor_base.xacro

python/example_robot_data/__init__.py

python/example_robot_data/robots_loader.py