Switch to storing To addresses as a slice

- Changes on-disk storage format
- Changes JSON API
- To and From values are now parsed/formatted by Go's mail.ParseAddress
  function
- Fixed bug in list-entry-template, was not escaping HTML characters
- Updated tests

themes/bootstrap/templates/mailbox/_show.html

@@ -53,7 +53,12 @@
       <dt>From:</dt>
       <dd>{{.message.From}}</dd>
       <dt>To:</dt>
-      <dd>{{.message.To}}</dd>
+      <dd>
+      {{range $i, $addr := .message.To}}
+        {{- if $i}},{{end}}
+        {{$addr -}}
+      {{end}}
+      </dd>
       <dt>Date:</dt>
       <dd>{{.message.Date}}</dd>
       <dt>Subject:</dt>

themes/bootstrap/templates/mailbox/index.html

@@ -15,9 +15,9 @@ $(document).ready(function() {
 <script type="text/html" id="list-entry-template">
   <button data-id="id" type="button" class="message-list-entry list-group-item">
     <div class="row">
-      <div class="col-sm-4 col-md-12 text-primary" data-content="subject"
+      <div class="col-sm-4 col-md-12 text-primary" data-content-text="subject"
         data-format="subject"/>
-      <div class="col-sm-4 col-md-12 small" data-content="from"/>
+      <div class="col-sm-4 col-md-12 small" data-content-text="from"/>
       <div class="col-sm-4 col-md-12 small" data-content="date" data-format="date"/>
     </div>
   </button>
@@ -34,8 +34,8 @@ $(document).ready(function() {
 <div class="col-md-3">
   <div class="input-group">
     <input id="message-search"
-           type="search" 
-           class="form-control" 
+           type="search"
+           class="form-control"
            placeholder="search"
            data-toggle="tooltip"
            data-placement="top"