Add option to disable notification light

Closes #91

src/main/java/org/tasks/Notifier.java

@@ -270,12 +270,16 @@ public class Notifier {
 
     private void activateNotification(int ringTimes, int notificationId, Notification notification, String text) {
         if (preferences.getBoolean(R.string.p_rmd_persistent, true)) {
-            notification.flags |= Notification.FLAG_NO_CLEAR | Notification.FLAG_SHOW_LIGHTS;
+            notification.flags |= Notification.FLAG_NO_CLEAR;
+        }
+        if (preferences.getBoolean(R.string.p_disable_notification_light, false)) {
+            notification.ledOffMS = 0;
+            notification.ledOnMS = 0;
+        } else {
+            notification.flags |= Notification.FLAG_SHOW_LIGHTS;
             notification.ledOffMS = 5000;
             notification.ledOnMS = 700;
             notification.ledARGB = Color.YELLOW;
-        } else {
-            notification.defaults = Notification.DEFAULT_LIGHTS;
         }
 
         if (atLeastJellybean()) {

src/main/res/values/keys.xml

@@ -243,6 +243,7 @@
   <string name="p_reverse_sort">reverse_sort</string>
   <string name="p_manual_sort">manual_sort</string>
   <string name="p_notification_priority">notification_priority</string>
+  <string name="p_disable_notification_light">disable_notification_light</string>
 
   <string-array name="TEA_control_sets_prefs">
         <item>@string/TEA_ctrl_when_pref</item>

src/main/res/values/strings.xml

@@ -137,6 +137,7 @@
     <string name="anonymous_usage_blurb">Anonymous usage statistics are collected</string>
     <string name="opt_out">Opt-out</string>
     <string name="tag_already_exists">Tag already exists</string>
+    <string name="disable_notification_light">Disable notification light</string>
 
     <string-array name="sync_SPr_interval_entries">
         <!-- sync_SPr_interval_entries: Synchronization Intervals -->

src/main/res/xml/preferences_reminders.xml

@@ -33,6 +33,11 @@
         android:showDefault="true"
         android:showSilent="true"
         android:title="@string/sound" />
+    <CheckBoxPreference
+        android:defaultValue="false"
+        android:dependency="@string/p_rmd_enabled"
+        android:key="@string/p_disable_notification_light"
+        android:title="@string/disable_notification_light" />
     <com.todoroo.astrid.ui.MultilineCheckboxPreference
         android:defaultValue="true"
         android:dependency="@string/p_rmd_enabled"