Battery discharge model: wrong xml tag

[alierum]

In the robot's text definition, i.e. eyebot_entity.cpp the battery uses the attribute "model"

<battery model=\"time_motion\" time_factor=\"1e-5\"\n"
                                  pos_factor=\"1e-3\"\n"
                                  orient_factor=\"1e-3\"/>\n

However, in battery_equipped_entity.cpp the attibute name is "discharge_model"

GetNodeAttributeOrDefault(t_tree, "discharge_model", strDischargeModel, strDischargeModel);

Which is the correct attribute ("model" doesn't work), so the help texts in all the *_entitiy.cpp files should be updated.

[jharwell]

The code says discharge_model, so that's probably what it should be.