Show inbound messages on the dashboard

This commit adds two things:

a section on the dashboard to show how many inbound messages the
service has received in the last 7 days, and how recently an inbound
message has been received
---

Doesn’t show the contents of any messages, just like how the rest of the
dashboard is an aggregation, never individual messages.

a page to show all the inbound messages the service has received in
the last 7 days
---

This shows the first line of the message. Eventually this will link
through to a ‘conversation’ page, where a service can see all the
messages it’s received from a given phone number.

app/assets/stylesheets/components/big-number.scss

@@ -129,3 +129,26 @@
   }
 
 }
+
+.big-number-meta-wrapper {
+
+  position: relative;
+  margin: $gutter-half 0 $gutter 0;
+  background: $govuk-blue;
+
+  .big-number-meta {
+
+    padding: ($gutter / 3) $gutter-half;
+    color: $white;
+    pointer-events: none;
+
+    @include media(desktop) {
+      position: absolute;
+      bottom: 7px;
+      right: 5px;
+      text-align: right;
+    }
+
+  }
+
+}

app/assets/stylesheets/components/table.scss

@@ -210,3 +210,11 @@ a.table-show-more-link {
   border-bottom: 1px solid $border-colour;
   padding: 0.75em 0 0.5625em 0;
 }
+
+.wide-left-hand-column {
+  display: block;
+  max-width: 560px;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}

app/assets/stylesheets/views/dashboard.scss

@@ -94,3 +94,7 @@
   }
 
 }
+
+.align-with-message-body {
+  margin-top: $gutter * 5 / 6;
+}