Switch to long document output names

This changes the names of the output files in doxygen.

If we have more stable urls then we can conventionally switch documenation versions more reliably.  /Documentation/HEAD/classes.html
/Documentation/1_3_1/classes.html

It would also be more stable for search engines.

they look like this
```
annotated.html                                                     class_urho3_d_1_1_tool_tip.html
_a_p_i_differences.html                                            class_urho3_d_1_1_tool_tip-members.html
_attribute_animation.html                                          class_urho3_d_1_1_u_i_batch.html
_attribute_list.html                                               class_urho3_d_1_1_u_i_batch-members.html
_audio.html                                                        class_urho3_d_1_1_u_i_element.html
_auxiliary_views.html                                              class_urho3_d_1_1_u_i_element-members.html
_building.html                                                     class_urho3_d_1_1_u_i.html
classes.html                                                       class_urho3_d_1_1_u_i-members.html
classrapidjson_1_1_generic_document.html                           class_urho3_d_1_1_unknown_component.html
classrapidjson_1_1_generic_value.html                              class_urho3_d_1_1_unknown_component-members.html
classrapidjson_1_1_memory_pool_allocator.html                      class_urho3_d_1_1_value_animation.html
class_urho3_d_1_1_allocator.html                                   class_urho3_d_1_1_value_animation_info.html
class_urho3_d_1_1_allocator-members.html                           class_urho3_d_1_1_value_animation_info-members.html
class_urho3_d_1_1_animatable.html                                  class_urho3_d_1_1_value_animation-members.html
class_urho3_d_1_1_animatable-members.html                          class_urho3_d_1_1_variant.html
class_urho3_d_1_1_animated_model.html                              class_urho3_d_1_1_variant-members.html
class_urho3_d_1_1_animated_model-members.html                      class_urho3_d_1_1_vector2.html
class_urho3_d_1_1_animated_sprite2_d.html                          class_urho3_d_1_1_vector2-members.html
class_urho3_d_1_1_animated_sprite2_d-members.html                  class_urho3_d_1_1_vector3.html
class_urho3_d_1_1_animation2_d.html                                class_urho3_d_1_1_vector3-members.html
class_urho3_d_1_1_animation2_d-members.html                        class_urho3_d_1_1_vector4.html
class_urho3_d_1_1_animation_controller.html                        class_urho3_d_1_1_vector4-members.html
class_urho3_d_1_1_animation_controller-members.html                class_urho3_d_1_1_vector_base.html
class_urho3_d_1_1_animation.html                                   class_urho3_d_1_1_vector_base-members.html
class_urho3_d_1_1_animation-members.html                           class_urho3_d_1_1_vector_buffer.html
class_urho3_d_1_1_animation_set2_d.html                            class_urho3_d_1_1_vector_buffer-members.html
class_urho3_d_1_1_animation_set2_d-members.html                    class_urho3_d_1_1_vector.html
class_urho3_d_1_1_animation_state.html                             class_urho3_d_1_1_vector-members.html
class_urho3_d_1_1_animation_state-members.html                     class_urho3_d_1_1_vertex_buffer.html
class_urho3_d_1_1_application.html                                 class_urho3_d_1_1_vertex_buffer-members.html
class_urho3_d_1_1_application-members.html                         class_urho3_d_1_1_view3_d.html
class_urho3_d_1_1_area_allocator.html                              class_urho3_d_1_1_view3_d-members.html
class_urho3_d_1_1_area_allocator-members.html                      class_urho3_d_1_1_view.html
```