… only one.

RobotHWGroup to have identical interfaces.  It accomplishes this
by combining interfaces during a InterfaceManager::get<T>() call.
This new combined interface is saved internally, but distinct
from other interface instances, so that while each interface keeps
its integrity, the RobotHWGroup::get<T>() call combines them all into
a new interface from which all ResourceHandles may be obtained.

Adolfo:
The new getHandles() and registerHandles(...) methods of ResourceManager are not strictly needed. You could get away with getNames() and a loop around getHandle(name) with no public API additions.

…Manager to this effect.

…o base class InterfaceManager.

…n original get<T>() call

so that if new interfaces are registered in the meantime, you will make new combined interfaces
for the new get calls to use.  Thus, every get call will only have a ResourceManager with handles
from only those interfaces registered up to that call.

…s suggestion.

…you to use 2 templated interfaces, instead of only 1.

… controller. (multi_controller.h)

Conflicts:
	hardware_interface/include/hardware_interface/internal/hardware_resource_manager.h

make rostest in CMakeLists optional (ros/rosdistro#3010)

…ommanding a velocity and acceleration.

This replaces all instances of ControllerInfo::hardware_interface
with std::set<std::string> hardware_interfaces instead.  This
allows one to properly represent multi-controllers which use
different types of interfaces.  getHardwareInterfaceType is
also converted to getHardwareInterfaceTypes.  A legacy version
of getHardwareInterfaceType is added which calls the other and
returns a random interface.  A warning is displayed if there is more
than one interface available. The ControllerState message is also
affected.