Added blogPath in the commenting functionality.

Added `blogPath` in the commenting functionality so calls to the `comment.ashx` doesn't 404 when in an virtual directory.

Although now this `var path = !string.IsNullOrWhiteSpace(Blog.BlogPath) ? "/" + Blog.BlogPath : "";` exists in both `CommentForm.cshtml` and `AdminMenu.cshtml`.
This code probably is unecessary anyway if the slash is already added in `blog:path` and Razor should handle null values, due to missing the element, without problems.

I made some changes regarding the above and to enable `data-blog-path` sharing between the script-files in this fredrikeriksson@ef8004dd708b8d79a31895b823fe7357e6346355 branch.
If the changes seems alright I'll merge them to this branch, if not, just take this as is.