Core/Units:

- Implement UNIT_FIELD_HOVERHEIGHT (requires DB data). This field, sent in update object packet, will determine the height at which a creature hovers if it has movementflag_hover applied. Note that hovering will now update the server-sided z-coordinate by the value of this field, and that all subsequent positional updates to the client will need to send z coordinate MINUS the hover height offset, or the hoverheight will be visually doubled client side.
- Correct our usage of movementflag_flying, movementflag_can_fly, movementflag_hover and movementflag_disable_gravity (previously levitate), and how they relate to InhabitType in the database. This fixes "flying creatures on steroids" bug (wings flapping too fast), and potentially a lot of visual issues in AI scripts. Note that a lot of scripts still set wrong movementflags, these need to be fixed on a case by case basis.
- Send correct packets for SPELL_AURA_FEATHER_FALL, SPELL_AURA_WATER_WALK and SPELL_AURA_HOVER apply/unapply.
- Send correct packet contents for movement update in Unit::SetSpeed.
- Misc. cleanup in affected scripts.

src/server/scripts/Northrend/Naxxramas/boss_sapphiron.cpp

@@ -296,7 +296,7 @@ public:
                     {
                         case EVENT_LIFTOFF:
                             me->HandleEmoteCommand(EMOTE_ONESHOT_LIFTOFF);
-                            me->SetLevitate(true);
+                            me->SetDisableGravity(true);
                             me->SendMovementFlagUpdate();
                             events.ScheduleEvent(EVENT_ICEBOLT, 1500);
                             iceboltCount = RAID_MODE(2, 3);
@@ -340,7 +340,7 @@ public:
                             return;
                         case EVENT_LAND:
                             me->HandleEmoteCommand(EMOTE_ONESHOT_LAND);
-                            me->SetLevitate(false);
+                            me->SetDisableGravity(false);
                             me->SendMovementFlagUpdate();
                             events.ScheduleEvent(EVENT_GROUND, 1500);
                             return;