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/Outland/shadowmoon_valley.cpp

@@ -223,7 +223,7 @@ public:
                 me->setFaction(FACTION_DEFAULT);
 
             FlyTimer = 10000;
-            me->SetLevitate(false);
+            me->SetDisableGravity(false);
             me->SetVisible(true);
         }
 
@@ -270,7 +270,7 @@ public:
                     PlayerGUID = 0;
                 }
                 me->SetVisible(false);
-                me->SetLevitate(false);
+                me->SetDisableGravity(false);
                 me->DealDamage(me, me->GetHealth(), NULL, DIRECT_DAMAGE, SPELL_SCHOOL_MASK_NORMAL, NULL, false);
                 me->RemoveCorpse();
             }
@@ -308,7 +308,7 @@ public:
                                     pos.m_positionZ += 25;
                                 }
 
-                                me->SetLevitate(true);
+                                me->SetDisableGravity(true);
                                 me->GetMotionMaster()->MovePoint(1, pos);
                             }
                         }
@@ -808,7 +808,7 @@ public:
             case 19: DoScriptText(LORD_ILLIDAN_SAY_7, Illi); return 5000; break;
             case 20:
                 Illi->HandleEmoteCommand(EMOTE_ONESHOT_LIFTOFF);
-                Illi->SetLevitate(true);
+                Illi->SetDisableGravity(true);
                 return 500; break;
             case 21: DoScriptText(OVERLORD_SAY_5, me); return 500; break;
             case 22: