Issue #431 - Prevent comment link expiry - Added functionality for comment linking

*   `media.html`
    *   Changed comment textarea handle from `comment` => `field_comment`
    *   Active comment is hilighted with the CSS class name `comment_active`
    	and also with the hyperlink anchor #comment
    *   Changed media.html so that pagination always uses
    	Route('mediagoblin.user_pages.media_home') as base_url
*   `user_pages/forms.py`
    *   Renamed MediaComment form field `comment` => `field_comment`
*   `user_pages/routing.py`
    *   Added route for `/u/joar/m/123..456/c/234..567/`, points to `media_home`
*   `user_pages/views.py`
    *   `media_home` now checks if the request contains a comment id parameter
        then acts accordingly with pagination whether to call it with a
        `jump_to_id` or not.
    *	`media_post_comment` - Updated MediaCommentForm field name
        `comment` => `field_comment`
*   `util.py`
    *   `redirect` now supports querystring arguments. - NOT USED (should we
        keep it? I think so, it might be useful, sometime [don't call me a
        code hoarder]).
    *   `Pagination.__init__` now accepts one further argument, the `jump_to_id`.
        It assist the comment linking functionality in finding and returning the
        proper page for a comment.
        This feature will work for all kinds of objects. It might not be
        optimal, but it is well functional :)

mediagoblin/user_pages/forms.py

@@ -17,5 +17,5 @@
 import wtforms
 
 class MediaCommentForm(wtforms.Form):
-	comment = wtforms.TextAreaField('Comment',
-    	[wtforms.validators.Required()])
+	field_comment = wtforms.TextAreaField('Comment',
+    	[wtforms.validators.Required()])

mediagoblin/user_pages/routing.py

@@ -24,6 +24,9 @@ user_routes = [
     Route('mediagoblin.user_pages.media_home', '/{user}/m/{media}/',
         requirements=dict(m_id="[0-9a-fA-F]{24}"),
         controller="mediagoblin.user_pages.views:media_home"),
+    Route('mediagoblin.user_pages.media_home.view_comment',
+          '/{user}/m/{media}/c/{comment}/',
+          controller="mediagoblin.user_pages.views:media_home"),
     Route('mediagoblin.edit.edit_media', "/{user}/m/{media}/edit/",
         controller="mediagoblin.edit.views:edit_media"),
     Route('mediagoblin.user_pages.atom_feed', '/{user}/atom/',

mediagoblin/user_pages/views.py

@@ -95,8 +95,14 @@ def media_home(request, media, page, **kwargs):
     """
     'Homepage' of a MediaEntry()
     """
+    if ObjectId(request.matchdict.get('comment')):
+        pagination = Pagination(
+            page, media.get_comments(), MEDIA_COMMENTS_PER_PAGE,
+            ObjectId(request.matchdict.get('comment')))
+    else:
+        pagination = Pagination(
+            page, media.get_comments(), MEDIA_COMMENTS_PER_PAGE)
 
-    pagination = Pagination(page, media.get_comments(), MEDIA_COMMENTS_PER_PAGE)
     comments = pagination()
 
     comment_form = user_forms.MediaCommentForm(request.POST)
@@ -118,7 +124,7 @@ def media_post_comment(request):
     comment = request.db.MediaComment()
     comment['media_entry'] = ObjectId(request.matchdict['media'])
     comment['author'] = request.user['_id']
-    comment['content'] = request.POST['comment']
+    comment['content'] = request.POST['field_comment']
 
     comment['content_html'] = cleaned_markdown_conversion(comment['content'])