Some more minor UI edits to install screens (#577)

Author: frostbitten

public/css/bootstrap-custom.css

@@ -1,4 +1,4 @@
- @font-face {
+@font-face {
    font-family: 'Glyphicons Halflings';
 
    src: url('fonts/glyphicons-halflings-regular.eot');

userfrosting/templates/themes/default/install/install-errors.twig

@@ -17,7 +17,7 @@
         <br>
         <div class="row">
             <div  class="col-xs-12 col-sm-4 col-md-6" >
-                <img class="img-fluid" src="{{site.uri.image}}/stuck.jpg">
+                <img class="img-fluid m-x-auto" src="{{site.uri.image}}/stuck.jpg">
             </div>
             <div class="col-xs-12 col-sm-8 col-md-6">
                 <p class="h3 text-center">Please fix the following errors, then <a href="{{site.uri.public}}/install">reload</a>.</p>

userfrosting/templates/themes/default/install/install-ready.twig

@@ -14,9 +14,9 @@
     <div class="container">
         <h1 class = "text-center">Congratulations.<br><small>UserFrosting is ready to rock.</small></h1>
         <br>
-        <div class="row">
+        <div class="row p-b-1">
             <div  class="col-xs-12 col-sm-4 col-lg-6" >
-                <img class="img-fluid m-b-1" src="{{site.uri.image}}/install-ready.jpg">
+                <img class="img-fluid m-b-1 m-x-auto" src="{{site.uri.image}}/install-ready.jpg">
             </div>
             <div class="col-xs-12 col-sm-8 col-lg-6">
                 {% for message in messages %}