Add sleep tracking, statistics module and backup features

Features:
- Sleep tracking with timer and manual duration input
- Statistics module with 5 tabs (daily summary, feeding, diapers, sleep, growth)
- Export/Import backup functionality in settings
- Complete German, French and Italian translations

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

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:id="@android:id/background">
+        <shape>
+            <corners android:radius="4dp"/>
+            <solid android:color="#33FFFFFF"/>
+        </shape>
+    </item>
+    <item android:id="@android:id/progress">
+        <clip>
+            <shape>
+                <corners android:radius="4dp"/>
+                <solid android:color="@color/accent"/>
+            </shape>
+        </clip>
+    </item>
+</layer-list>