Add support for review comments.

[1] 

The review object now supports comments. The comment is optional.

**POST /api/event/&lt;key&gt;/review**

````json
{"rating":{"value":3.5}, "comment":"a review comment"}
````

[2] 

For all users that specified review comments, there is a JSON api to fetch those comments along with the name of the user, etc.

**GET /api/event/&lt;key&gt;/review_comment_view?limit=N**
* supports pagination
* ordered by comment creation date.
* only reviews with comments are shown.

````xml
<listResponseMsg>
  <data xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="reviewCommentView">
    <authorInfo>
      <eventOrganizerRating>
        <count>0</count>
        <sum>0.0</sum>
      </eventOrganizerRating>
      <firstName>Susan</firstName>
      <karmaPoints>0</karmaPoints>
      <key>aglrYXJtYWRlbW9yIQsSBFVzZXIiFzEwMDAwNjA3NDM3Njk1N2ZhY2Vib29rDA</key>
      <lastName>Liangberg</lastName>
      <profileImage>
        <url>https://graph.facebook.com/100006074376957/picture</url>
        <urlProvider>FACEBOOK</urlProvider>
      </profileImage>
    </authorInfo>
    <comment>second review comment (v2)!</comment>
    <commentCreationDate>2013-06-10T14:32:02.382-07:00</commentCreationDate>
    <rating>
      <value>2.0</value>
    </rating>
  </data>
</listResponseMsg>
````

Future note:

Right now we don't support anonymous comments. We could support anonymous comments in the future... however if there aren't many people who are reviewing it'll be pretty easy to figure out who said what. I think if someone wants to leave a public comment they should be willing to put their name on it. That's the google+/zagat review philosophy.