Asynchronously load contacts to improve responsiveness

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

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="oval">
+
+    <solid
+        android:color="@color/colorAccent"/>
+
+    <size
+        android:width="40dp"
+        android:height="40dp"/>
+</shape>

app/src/main/res/layout/subscription_row.xml

@@ -29,7 +29,7 @@
         android:layout_alignParentStart="true"
         android:layout_alignParentTop="true"
         android:layout_margin="16dp"
-        android:src="@color/colorAccent"
+        android:src="@drawable/avatar_placeholder"
         tools:ignore="ContentDescription"/>
 
     <TextView

app/src/main/res/values/strings.xml

@@ -65,7 +65,7 @@
     <string name="pubkey_available">Public key available</string>
     <string name="pubkey_not_available">Public key not yet available</string>
     <string name="alt_qr_code">QR code</string>
-    <string name="add_identity_warning">Having more identities will reequire more resources. If you are sure you want to add an identity, please select what exactly you want to do:</string>
+    <string name="add_identity_warning">Having more identities will require more resources. If you are sure you want to add an identity, please select what exactly you want to do:</string>
     <string name="share">Share</string>
     <string name="delete_identity_warning">Are you sure you want to delete this identity? You won\'t be able to receive any messages sent to this address and can\'t undo this operation.</string>
     <string name="delete_contact_warning">Are you sure you want to delete this contact?</string>