Add quick-start assistant for new users (#833)

* First draft for quick-setup

* Add payment

* Fix stripe w/o connect

* cols

* Add tests

src/pretix/static/pretixcontrol/scss/main.scss

@@ -128,6 +128,10 @@ h1 .btn-sm {
     padding-top: 20px;
 }
 
+p.bigger {
+    font-size: 16px;
+}
+
 .helper-display-block {
     display: block !important;
 }
@@ -468,7 +472,33 @@ body.loading #wrapper {
         text-decoration: none;
     }
 }
+.quick-setup-step {
+    clear: both;
+    .quick-icon {
+        float: left;
+        width: 100px;
 
+        .fa-ticket, .fa-check-circle {
+            margin-top: -20px;
+        }
+        .fa-wrench {
+            margin-top: -30px;
+        }
+        .fa-money, .fa-envelope {
+            margin-top: -40px;
+        }
+    }
+    .quick-icon .fa {
+        font-size: 100px;
+        line-height: 170px;
+        display: block;
+    }
+    .quick-content {
+        margin-left: 160px;
+        padding-top: 5px;
+        overflow: hidden;
+    }
+}
 .thank-you {
     margin-bottom: 25px;
 
@@ -503,6 +533,16 @@ body.loading #wrapper {
         }
     }
 }
+@media (max-width: $screen-md-max) {
+    .quick-setup-step {
+        .quick-icon {
+            display: none;
+        }
+        .quick-content {
+            margin-left: 0;
+        }
+    }
+}
 @media (max-width: $screen-sm-max) {
     .thank-you {
         text-align: center;