Fix for blog index page.
Changed model so that every blog entry from the getAll method (used in actions/index.php) will now also contain a boolean value 'allow_comments'.
This will be set to true when:
- the setting allow_comments for that blog entry is true
- the general blog module setting allow_comments is also true

Changed index.tpl: The comment links will only be shown when allow_comments for that blog entry is true.
Fix for recent_articles_full widget.
Only change necessary was to add a check on widgetBlogRecentArticlesFull.allow_comments. Because it uses the same getAll method from the model as the index.tpl template which was fixed in previous commit.
Fix for blog category page.
Every blog entry from the getAllForCategory method in model now also contains the boolean value 'allow_comments'.
This will be set to true when:
- the setting allow_comments for that blog entry is true
- the general blog module setting allow_comments is also true
Fix for blog entry detail page.
Here a check was already in place for displaying/hiding the section to add a comment.
I added a check on:
- listitem that displays info about the comments.
- the section that displays the existing comments for that blog entry.
Fix for archive page.
Every blog entry from the getAllForDateRange method in model now also contains the boolean value 'allow_comments'.
Added a variable to archive action called 'allowComments'. This is a boolean to indicate that the archive may display comment info at all. It reflects the value that is set in the global blog module setting for allow comments.
Modified archive template:
- added check around th. Won't be displayed when global blog setting comments_allowed is false.
- added check around td. It won't be displayed when the global blog setting comments_allowed is false or when the blog entry setting comments_allowed is false.
Merge pull request #345 from KoenHeye/issues/334

Issues/334