Fix warnings build errors (#822)

* Remove warning messages.

* Fix build errors.

* Fix ARTableTop scene - wrong shaders

* Resave Pngs without ETC1 compression

Author: abhishektrip

sdkproject/Assets/Mapbox/Resources/MapboxStyles/Styles/MapboxSampleStyles/Dark/DarkIcon.png

@@ -3,8 +3,6 @@
 	using System;
 	using Mapbox.Unity.MeshGeneration.Modifiers;
 	using Mapbox.Unity.MeshGeneration.Data;
-	using UnityEngine;
-	using UnityEditor;
 
 	[Serializable]
 	public class GeometryMaterialOptions : ModifierProperties

sdkproject/Assets/Mapbox/Resources/MapboxStyles/Styles/MapboxSampleStyles/Fantasy/FantasyIcon.png

@@ -7,7 +7,6 @@
 	[CustomPropertyDrawer(typeof(MaterialList))]
 	public class MaterialListDrawer : PropertyDrawer
 	{
-		static float lineHeight = EditorGUIUtility.singleLineHeight;
 		public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
 		{
 			EditorGUI.BeginProperty(position, label, property);

sdkproject/Assets/Mapbox/Resources/MapboxStyles/Styles/MapboxSampleStyles/Light/LightIcon.png

@@ -18,9 +18,6 @@ public class VectorFilterOptionsDrawer : PropertyDrawer
 		private string[] descriptionArray;
 		static float lineHeight = EditorGUIUtility.singleLineHeight;
 		bool showFilters = true;
-		static bool _isInitialized = false;
-		static string cachedLayerName = "";
-		static bool dataUnavailable = false;
 
 		GUIContent operatorGui = new GUIContent { text = "Operator", tooltip = "Filter operator to apply. " };
 		GUIContent numValueGui = new GUIContent { text = "Num Value", tooltip = "Numeric value to match using the operator.  " };

sdkproject/Assets/Mapbox/Resources/MapboxStyles/Styles/MapboxSampleStyles/Realistic/RealisticIcon.png

@@ -17,7 +17,7 @@ public abstract class AbstractEditorLocationProvider : AbstractLocationProvider
 		[SerializeField]
 		bool _sendEvent;
 
-		WaitForSeconds _wait;
+		WaitForSeconds _wait = new WaitForSeconds(0);
 
 #if UNITY_EDITOR
 		protected virtual void Awake()