Make the sorting button more visible (Fix #137)

app/src/main/java/com/fox2code/mmm/module/ModuleViewAdapter.java

@@ -190,6 +190,7 @@ public final class ModuleViewAdapter extends RecyclerView.Adapter<ModuleViewAdap
             if (moduleHolder.isModuleHolder()) {
                 this.canExpand = false;
                 this.buttonAction.setVisibility(View.GONE);
+                this.buttonAction.setBackground(null);
                 LocalModuleInfo localModuleInfo = moduleHolder.moduleInfo;
                 if (localModuleInfo != null) {
                     this.switchMaterial.setVisibility(View.VISIBLE);
@@ -286,10 +287,12 @@ public final class ModuleViewAdapter extends RecyclerView.Adapter<ModuleViewAdap
                 if (type == ModuleHolder.Type.SEPARATOR && moduleHolder.filterLevel != 0) {
                     this.buttonAction.setVisibility(View.VISIBLE);
                     this.buttonAction.setImageResource(moduleHolder.filterLevel);
+                    this.buttonAction.setBackgroundResource(R.drawable.bg_baseline_circle_24);
                 } else {
                     this.buttonAction.setVisibility(
                             type == ModuleHolder.Type.NOTIFICATION ?
                                     View.VISIBLE : View.GONE);
+                    this.buttonAction.setBackground(null);
                 }
                 this.switchMaterial.setVisibility(View.GONE);
                 this.creditText.setVisibility(View.GONE);

app/src/main/res/drawable/bg_baseline_circle_24.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="32dp"
+    android:height="32dp"
+    android:tint="?attr/colorAccent"
+    android:alpha="0.9"
+    android:viewportHeight="24"
+    android:viewportWidth="24">
+    <path android:fillColor="@android:color/white" android:pathData="M12,2C6.47,2 2,6.47 2,12s4.47,10 10,10 10,-4.47 10,-10S17.53,2 12,2z"/>
+</vector>