Bug 1372486 - Part 4: Create a dummy files for empty resource folders. r=nalexander,nechen

Since Mercurial doesn't support empty folder, a dummy file is added to each res folders.
These files should be removed after we put Photon/Australis specific resources in their own res folders.

MozReview-Commit-ID: FYgaDgMWHBb

--HG--
extra : rebase_source : ca344187cd9f359277e5de7f8406974edb2060b8

mobile/android/app/lint.xml

@@ -222,6 +222,8 @@
              preprocessed_resources res/raw folder. Lint reports it as unused. We should get
              rid of the file eventually. See bug 1268948. -->
         <ignore path="**/raw/.mkdir.done" />
+        <ignore path="src/australis/res/values/skin_strings.xml"/>
+        <ignore path="src/photon/res/values/skin_strings.xml"/>
     </issue>
     <issue id="Usability" severity="error" />
     <issue id="UseCheckPermission" severity="error" />

mobile/android/app/src/australis/res/values/skin_strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<resources>
+  <string name="skin">australis</string>
+</resources>

mobile/android/app/src/photon/res/values/skin_strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<resources>
+  <string name="skin">photon</string>
+</resources>