fix(send): use a placeholder instead of an identicon for "add a contact"

www/img/contact-placeholder.svg

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Generator: Adobe Illustrator 21.0.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
+<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
+	 viewBox="0 0 35 35" style="enable-background:new 0 0 35 35;" xml:space="preserve">
+<style type="text/css">
+	.st0{opacity:0.1;}
+</style>
+<path class="st0" d="M17.5,0C7.9,0,0,7.9,0,17.5s7.9,17.5,17.5,17.5S35,27.1,35,17.5S27.1,0,17.5,0L17.5,0z M28.6,26.9
+	c-1-2.3-3.2-3.3-5.4-4.1c-1-0.3-1.6-1.3-1.8-2.2c1.9-1.2,3.4-3.5,3.4-6.1v-1.5c0-4.1-3.2-7.3-7.3-7.3s-7.3,3.2-7.3,7.3v1.5
+	c0,2.6,1.5,4.9,3.5,6.3C13.4,21.7,13,22.5,12,23c-2.2,0.7-4.4,1.7-5.4,4.1c-2.3-2.6-3.6-6-3.6-9.6c0-8,6.6-14.5,14.6-14.5
+	s14.6,6.5,14.6,14.5C32.1,21.1,30.8,24.4,28.6,26.9L28.6,26.9z"/>
+</svg>

www/views/tab-send.html

@@ -41,7 +41,7 @@
         <div class="list">
           <a class="item item-icon-left item-icon-right" ng-if="!hasContacts" ui-sref="tabs.send.addressbook">
             <i class="icon big-icon-svg">
-              <gravatar class="send-gravatar" name="" width="30" email=""></gravatar>
+              <img src="img/contact-placeholder.svg" class="bg"/>
             </i>
             <span translate>Add a Contact</span>
             <i class="icon bp-arrow-right"></i>