Update Unity version to 2018.3.0f2

Author: mattatz

.gitignore

@@ -2,6 +2,7 @@
 [Tt]emp/
 [Oo]bj/
 [Bb]uild/
+Logs/
 Papers/
 .vs/
 

Assets/Packages/Voxelizer/Demo/Materials/VolumeTest.mat

@@ -4,8 +4,9 @@
 Material:
   serializedVersion: 6
   m_ObjectHideFlags: 0
-  m_PrefabParentObject: {fileID: 0}
-  m_PrefabInternal: {fileID: 0}
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
   m_Name: VolumeTest
   m_Shader: {fileID: 4800000, guid: 7bbc58d2cfa1440408c770bae505c98c, type: 3}
   m_ShaderKeywords: