fix user keys layout, adjust @media breakpoints to bs4, fix more unused css, optimize script

hosting/templates/hosting/choice_ssh_keys.html

@@ -25,7 +25,6 @@
                             {% trans "Generate" %}
                         </button>
                     </form>
-
                 </div>
                 <div>
                     <h2>{% trans "Using existing key" %}</h2>

hosting/templates/hosting/user_key.html

@@ -4,7 +4,7 @@
 <div>
 	<div class="virtual-machine-container dashboard-container">
 		<div class="row">
-			<div class="col-md-9 col-md-offset-2">
+			<div class="col-md-8 col-md-offset-2">
                 <form method="POST" action="" novalidate class="form-ssh">
                     {% csrf_token %}
                     <div class="page-header">