Mail improvements: - Implement new config option in mail-section "ignore_alternatives" to ignore alternatives in a multipart/alternative mail. The *last* text/plain part of the *first* multipart/alternative is used as the message, if ignore_alternatives is set all other alternative parts of the first multipart/alternative that contained a text/plain part are ignored. Other multipart/alternative or other multipart are attached as before. This fixes [SF#959811] "Multipart/alternative handling considered bad". Note that this also changes which text/plain part is attached as the message if there are several text/plain parts in a multipart: Previously the *first* text/plain would be attached. Now we attach the *last* one, this is more in line with rfc 2046, sec. 5.1.4. according to Philipp Gortan. - Fix bug in attachment of text parts: If there are multiple text/plain parts in a nested multipart, the previous code would attach the multipart serialisation instead of the text/plain serialisation as a file to the issue in some cases. - Add regression tests for the new config-option and bug-fixes above.

<tal:block metal:use-macro="templates/page/macros/icing">
<title metal:fill-slot="head_title" i18n:translate=""
 >List of messages - <span tal:replace="config/TRACKER_NAME"
 i18n:name="tracker"/></title>
<span metal:fill-slot="body_title" tal:omit-tag="python:1"
 i18n:translate="">Message listing</span>
<td class="content" metal:fill-slot="content">
<table tal:define="batch request/batch" class="messages">
 <tr><th colspan=2 class="header" i18n:translate="">Messages</th></tr>
 <tal:block tal:repeat="msg batch">
  <tr>
   <th tal:content="string:Author: ${msg/author}">author</th>
   <th tal:content="string:Date: ${msg/date}">date</th>
  </tr>
  <tr>
   <td colspan="2"><pre tal:content="msg/content">content</pre></td>
  </tr>
 </tal:block>

 <metal:block use-macro="templates/issue.index/macros/batch-footer" />

</table>
</td>

</tal:block>