Go syntax highlighting support for IntelliJ/Goland 2019.2 (#70)

IntelliJ/Goland version 2019.2 introduced support for 20+ languages (1)
out-of-the-box by integrating TextMate schemes (2).
Unfortunately this resulted in a change for existing theme definition
where some editor color scheme keys that previously inherited the best
matching global key now used the attributes defined by the parent theme
_Darcula_. Therefore Nord's highlighting for Go broke and required to
explicitly define the values for some attributes in order to achieve
the same highlight like in previous versions that are matching Nord's
style guidelines.

References:
  (1) https://www.jetbrains.com/idea/whatsnew/#v2019-2-editor
  (2) https://macromates.com

Resolves GH-69

resources/themes/nord.xml

@@ -829,23 +829,57 @@
         <option name="FOREGROUND" value="81a1c1" />
       </value>
     </option>
+    <option name="GO_BAD_TOKEN">
+      <value>
+        <option name="BACKGROUND" value="bf616a" />
+        <option name="EFFECT_TYPE" value="2" />
+      </value>
+    </option>
+    <option name="GO_BLOCK_COMMENT" baseAttributes="DEFAULT_BLOCK_COMMENT" />
+    <option name="GO_BUILTIN_CONSTANT">
+      <value>
+        <option name="FOREGROUND" value="81a1c1" />
+      </value>
+    </option>
+    <option name="GO_BUILTIN_FUNCTION_CALL" baseAttributes="DEFAULT_FUNCTION_CALL" />
     <option name="GO_BUILTIN_TYPE_REFERENCE">
       <value>
         <option name="FOREGROUND" value="81a1c1" />
       </value>
     </option>
-    <option name="GO_LOCAL_CONSTANT">
+    <option name="GO_BUILTIN_VARIABLE">
       <value>
-        <option name="FOREGROUND" value="d8dee9" />
+        <option name="FOREGROUND" value="81a1c1" />
+        <option name="EFFECT_TYPE" value="1" />
+      </value>
+    </option>
+    <option name="GO_EXPORTED_FUNCTION" baseAttributes="DEFAULT_FUNCTION_DECLARATION" />
+    <option name="GO_EXPORTED_FUNCTION_CALL" baseAttributes="DEFAULT_FUNCTION_CALL" />
+    <option name="GO_EXPORTED_INTERFACE_REFERENCE">
+      <value>
+        <option name="FOREGROUND" value="8fbcbb" />
         <option name="FONT_TYPE" value="1" />
       </value>
     </option>
+    <option name="GO_KEYWORD" baseAttributes="DEFAULT_KEYWORD" />
+    <option name="GO_LINE_COMMENT" baseAttributes="DEFAULT_LINE_COMMENT" />
+    <option name="GO_LOCAL_FUNCTION" baseAttributes="DEFAULT_FUNCTION_DECLARATION" />
+    <option name="GO_LOCAL_FUNCTION_CALL" baseAttributes="DEFAULT_FUNCTION_CALL" />
+    <option name="GO_METHOD_RECEIVER" baseAttributes="DEFAULT_LOCAL_VARIABLE" />
+    <option name="GO_PACKAGE" baseAttributes="DEFAULT_IDENTIFIER" />
     <option name="GO_PACKAGE_EXPORTED_CONSTANT">
       <value>
         <option name="FOREGROUND" value="d8dee9" />
-        <option name="FONT_TYPE" value="3" />
+        <option name="FONT_TYPE" value="1" />
+      </value>
+    </option>
+    <option name="GO_PACKAGE_EXPORTED_VARIABLE">
+      <value>
+        <option name="FOREGROUND" value="d8dee9" />
+        <option name="EFFECT_TYPE" value="1" />
       </value>
     </option>
+    <option name="GO_TYPE_REFERENCE" baseAttributes="DEFAULT_CLASS_REFERENCE" />
     <option name="GRID_ERROR_VALUE">
       <value>
         <option name="FOREGROUND" value="bf616a" />