Merge branch 'new_descriptions' into 'devel'

CMakeLists.txt

double_pendulum_description/meshes/base_link.STL

double_pendulum_description/meshes/link1.STL

double_pendulum_description/meshes/link2.STL

double_pendulum_description/urdf/double_pendulum.urdf

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/__main__.py

python/example_robot_data/robots_loader.py