Show "Mark all as read" as action

Resolves #89

Author: tughi

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

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?colorControlNormal"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="#000000"
+        android:pathData="M18,7l-1.41,-1.41 -6.34,6.34 1.41,1.41L18,7zM22.24,5.59L11.66,16.17 7.48,12l-1.41,1.41L11.66,19l12,-12 -1.42,-1.41zM0.41,13.41L6,19l1.41,-1.41L1.83,12 0.41,13.41z" />
+</vector>

app/src/main/res/menu/entry_list_fragment.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<menu xmlns:android="http://schemas.android.com/apk/res/android">
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
     <item
         android:id="@+id/show_read_entries"
         android:checkable="true"
@@ -21,5 +22,7 @@
     </item>
     <item
         android:id="@+id/mark_all_read"
-        android:title="@string/action__mark_all_read" />
+        android:icon="@drawable/action_mark_all_done"
+        android:title="@string/action__mark_all_read"
+        app:showAsAction="ifRoom" />
 </menu>