Bump the official supported Unity version to 18.4. Fixes MLA-23 (#3121)

Author: surfnerd

.gitignore

@@ -1,9 +1,9 @@
 /UnitySDK/[Ll]ibrary/
+/UnitySDK/Logs/
 /UnitySDK/[Tt]emp/
 /UnitySDK/[Oo]bj/
 /UnitySDK/[Bb]uild/
 /UnitySDK/[Bb]uilds/
-/UnitySDK/[Pp]ackages/
 /UnitySDK/Assets/AssetStoreTools*
 /UnitySDK/Assets/Plugins*
 /UnitySDK/Assets/Demonstrations*

.yamato/csharp-tests.yml

@@ -1,5 +1,4 @@
 test_editors:
-  - version: 2017.4
   - version: 2018.4
   - version: 2019.3
 ---
@@ -8,7 +7,7 @@ test_mac_editmode_{{ editor.version }}:
   name: Test Mac EditMode {{ editor.version }}
   agent:
     type: Unity::VM::osx
-    image: ml-agents/ml-agents-bokken-mac:v0.1.2-440635
+    image: ml-agents/ml-agents-bokken-mac:v0.1.3-475350
     flavor: i1.small
   variables:
     UNITY_VERSION: {{ editor.version }}
@@ -18,7 +17,6 @@ test_mac_editmode_{{ editor.version }}:
     pull_requests:
       - targets:
           only:
-            - "develop"
             - "master"
             - "/release-.*/"
             - "/hotfix-.*/"

.yamato/standalone-build-test.yml

@@ -1,5 +1,4 @@
 test_editors:
-  - version: 2017.4
   - version: 2018.4
   - version: 2019.3
 ---
@@ -8,7 +7,7 @@ test_mac_standalone_{{ editor.version }}:
   name: Test Mac Standalone {{ editor.version }}
   agent:
     type: Unity::VM::osx
-    image: ml-agents/ml-agents-bokken-mac:v0.1.2-440635
+    image: ml-agents/ml-agents-bokken-mac:v0.1.3-475350
     flavor: i1.small
   variables:
     UNITY_VERSION: {{ editor.version }}
@@ -18,7 +17,6 @@ test_mac_standalone_{{ editor.version }}:
     pull_requests:
       - targets:
           only:
-            - "develop"
             - "master"
             - "/release-.*/"
             - "/hotfix-.*/"

UnitySDK/Assets/ML-Agents/Editor/Tests/StandaloneBuildTest.cs

@@ -9,7 +9,7 @@ namespace MLAgents
 {
     public class StandaloneBuildTest
     {
-        static void BuildStandalonePlayerOSX()
+        public static void BuildStandalonePlayerOSX()
         {
             string[] scenes = { "Assets/ML-Agents/Examples/3DBall/Scenes/3DBall.unity" };
             var buildResult = BuildPipeline.BuildPlayer(scenes, "testPlayer", BuildTarget.StandaloneOSX, BuildOptions.None);