add icons to the preference categories

Closes #2361

res/values/attrs.xml

@@ -88,4 +88,12 @@
         <attr name="android:foregroundInsidePadding" />
         <attr name="android:foregroundGravity" />
     </declare-styleable>
+
+    <attr name="pref_ic_push" format="reference" />
+    <attr name="pref_ic_sms_mms" format="reference" />
+    <attr name="pref_ic_notifications" format="reference" />
+    <attr name="pref_ic_app_protection" format="reference" />
+    <attr name="pref_ic_appearance" format="reference" />
+    <attr name="pref_ic_storage" format="reference" />
+    <attr name="pref_ic_advanced" format="reference" />
 </resources>

res/values/dimens.xml

@@ -13,4 +13,5 @@
     <dimen name="conversation_item_drop_shadow_dist">1.5dp</dimen>
     <dimen name="contact_selection_photo_size">50dp</dimen>
     <dimen name="thumbnail_max_size">230dp</dimen>
+    <dimen name="preference_fragment_padding_side">8dp</dimen>
 </resources>

res/values/themes.xml

@@ -95,6 +95,14 @@
         <item name="menu_save_icon">@drawable/ic_save_white_24dp</item>
 
         <item name="reminder_header_background">#ff1d85d7</item>
+
+        <item name="pref_ic_push">@drawable/ic_push_black</item>
+        <item name="pref_ic_sms_mms">@drawable/ic_message_black</item>
+        <item name="pref_ic_notifications">@drawable/ic_notifications_black</item>
+        <item name="pref_ic_app_protection">@drawable/ic_app_protection_black</item>
+        <item name="pref_ic_appearance">@drawable/ic_brightness_6_black</item>
+        <item name="pref_ic_storage">@drawable/ic_delete_black</item>
+        <item name="pref_ic_advanced">@drawable/ic_advanced_black</item>
     </style>
 
     <style name="TextSecure.DarkTheme" parent="@style/Theme.AppCompat">
@@ -184,6 +192,14 @@
         <item name="menu_save_icon">@drawable/ic_save_white_24dp</item>
 
         <item name="reminder_header_background">@color/textsecure_primary_dark</item>
+
+        <item name="pref_ic_push">@drawable/ic_push_gray</item>
+        <item name="pref_ic_sms_mms">@drawable/ic_message_gray</item>
+        <item name="pref_ic_notifications">@drawable/ic_notifications_gray</item>
+        <item name="pref_ic_app_protection">@drawable/ic_app_protection_gray</item>
+        <item name="pref_ic_appearance">@drawable/ic_brightness_6_gray</item>
+        <item name="pref_ic_storage">@drawable/ic_delete_gray</item>
+        <item name="pref_ic_advanced">@drawable/ic_advanced_gray</item>
     </style>
 
     <style name="TextSecure.Light.Dialog"

res/xml/preferences.xml

@@ -4,23 +4,30 @@
     <CheckBoxPreference android:defaultValue="false"
                         android:key="pref_toggle_push_messaging"
                         android:title="@string/preferences__use_data_channel"
-                        android:summary="@string/preferences__use_the_data_channel_for_communication_with_other_textsecure_users"/>
+                        android:summary="@string/preferences__use_the_data_channel_for_communication_with_other_textsecure_users"
+                        android:icon="?pref_ic_push"/>
 
     <Preference android:key="preference_category_sms_mms"
-                android:title="@string/preferences__sms_mms"/>
+                android:title="@string/preferences__sms_mms"
+                android:icon="?pref_ic_sms_mms"/>
 
     <Preference android:key="preference_category_notifications"
-                android:title="@string/preferences__notifications"/>
+                android:title="@string/preferences__notifications"
+                android:icon="?pref_ic_notifications"/>
 
     <Preference android:key="preference_category_app_protection"
-                android:title="@string/preferences__app_protection"/>
+                android:title="@string/preferences__app_protection"
+                android:icon="?pref_ic_app_protection"/>
 
     <Preference android:key="preference_category_appearance"
-                android:title="@string/preferences__appearance"/>
+                android:title="@string/preferences__appearance"
+                android:icon="?pref_ic_appearance"/>
 
     <Preference android:key="preference_category_storage"
-                android:title="@string/preferences__delete_old_messages"/>
+                android:title="@string/preferences__delete_old_messages"
+                android:icon="?pref_ic_storage"/>
 
     <Preference android:key="preference_category_advanced"
-                android:title="@string/preferences__advanced"/>
+                android:title="@string/preferences__advanced"
+                android:icon="?pref_ic_advanced"/>
 </PreferenceScreen>